Steel or Aluminium bikes: recommendations

Get a bike which can take 35-40mm tyres.  These sizes of tyres will allow you to use lower pressures and still have a fast, comfortable ride.  The Schwalbe G Ones either in 35mm or 40mm are fantastic tyres.  Boardman ASR 8.9 is a good bike.  I bought my daughter the HYB 8.6 which is very similar but with flat bars

Steel!

I own carbon race bikes, Caad 10/12’s and one day Ti.

For sheer fun and commuting/long distance: steel unless there are lots of climbs- although components could sort that.  I’m faster over 100 miles if not too hilly on my steel 9.2kg Charge Plug - buttery smooth.  Racing/hilly sportives I use my carbon TCR or CAAD with 25mm/compact gearing.

Racing: carbon unless you can afford 953 frames.

Ride quality vs. Ride speed. 

Ignore the frame material, decide how much you want to spend and the usage, then go from there.

Supple tyres and more volume make a huge difference to comfort (as do carbon bars and seatpost, in my experience).

Frame material comes after all those factors, so far, carbon frames have been the most comfortable I've ridden (super smooth, barely any road buzz and compliant) - but then I'd expect that from my carbon bikes given how much they cost - so I can't give a direct comparison between aluminium and carbon frames at the same price point.

There are some good steel bikes on Ebay. Go there and get a bargain, rather than something new and compromised.

https://www.ebay.co.uk/itm/JAMIS-QUEST-COMP-ROAD-RACER-BIKE-54-CM-REYNOL...

https://www.ebay.co.uk/itm/Custom-Steel-Race-Bike-Columbus-Futura-Dura-A...

I'll +1 a Genesis Croix de Fer. That's what I've been using for for commuting over the past year and it's really comfortable and has been solid mechanically.
It's great for longer club rides too - I thought it would be really slow being a bit on the heavy side but it's not been an issue at all.

the Green Commute Initiative (GCI) cycle 2 work scheme has no limit to value, so you can go over the £1,000 standard amount

you could then get a steel/titanium gravel style bike - they are great for commuting, as you can use the bigger tyres, making it easier to use on cycle paths etc

I'm not sure that you'll be able to tell the difference between a sub-GBP 1000 steel vs alloy frame.  The wheels and tyres (type and volume) will make more difference.  I have a Ti Litespeed and a steel Gios-both of which are very good frames, but even then the ride changes massively as I switch wheels around.  I fitted 28mm Conti 4 Seasons to the Gios (vs 25mm) and, again, the ride has changed becoming more comfortable. 

I'm not clear if it can be combined with the C2W scheme but another point in favour of the Boardman would be the 10% off you can get with CUK or British Cycling membership, e.g.

www.cyclinguk.org/member-benefits/halfords

And wait another 20 days before buying anything 

Genesis Croix de Fer has a solid reputation. 

https://road.cc/content/review/73063-genesis-croix-de-fer

How about the Ribble CGR's?  They have Aluminium and Steel versions at about £1k, and the reviews are pretty good...

https://www.ribblecycles.co.uk/ribble-cgr-725/

https://www.ribblecycles.co.uk/ribble-cgr-al/

Eyeing up a steel version myself...

Not sure how it would work with the cycle to work scheme but the Planet X London Road or London Road SL might be worth a look.  Several different version available with 1x and 2x and with hydraulic brakes all under £1k.

https://www.planetx.co.uk/c/q/bikes/road-bikes/london-road

The (steel frame/carbon fork) Boardman ASR 8.8 with disc brakes seems impressively quite light at only 11kg with mudguards according the Boardman website.
The new (aluminium frame/carbon fork) Triban RC520 (also disc brakes) was reviewed here recently and the review said it clocked 10.7kg on the scales. It doesn’t have mudguards (although they can be fit) so it looks like both those bikes are a very similar overall weight (and price).
The cheaper RC500 is probably only fractionally heavier but it seems that Disc brake fans don't speak so well of it's lesser quality (cable?) disc brakes when compared to the 520 model.

Fairlight is another uk brand that claims to do very light steel frames on their standard steel road bikes.. i think around 9.5kg....but I believe they are a bit pricier (nearer 1.5 grand) so maybe not for you.

What about the (aluminium frame/carbon fork) Btwin Triban 500? If you can live without disc brakes that one is only £349 and weighs in the same (10.7kg) as the above other bikes. I’ve used the Btwin Triban 500 for 16 months heavily and it’s a great all round bike for whatever you need to do (it even accepts slightly wider grippier tires if you want to quick-switch wheels and go on some off road trails). The only weak point is the quite poor caliper brakes (I just replace the pads frequently but maybe changing the very cheap unbranded calipers themselves would be a better way to go).

I’d be inclined to move quickly if you are interested in the current Btwin Triban range as they might be facing extinction soon given they are a few years old, the new RC models are out and Decathlon say they are dropping the Btwin name altogether on adult bikes.
It could also be worth looking at the Btwin Triban 520 and 540 models in that series which see the overall
weight drop even slightly more, largely due to lighter groupset I believe.
The decals are just stickers on the Btwin Triban 500 whereas on the 520 and 540 models the decals are painted on. Not that sticker decals really bother me in this case as the adhesive seems strong (none peeling away after 16 months) and you can always buy or reprint and replace stickers on a bike if you need to.

Personally, if I had a budget of £1000, I’d be looking for a lighter category of aluminium bike altogether (8-9kg) of which there would be quite a few options. In fact the Btwin Ultra 900 AF is 799,99 euros in most Decathlon Europe stores at the moment and it’s sub 9kg. Maybe that isn’t the best choice for you as the frame is quite racey positioned and you say you want to do commuting, but there are a lot of lightweight (8-9kg) aluminium road bikes out there today around the grand price point that do have the slightly more upright “touring” race bike position.

Canyon Endurace AL for example which starts at 899 euros on their website (6.0 model with Tiagra) and weighs under 9kg. I haven’t checked but I would guess that for UK customers it’s about £850?

If you are intent on disc brakes that changes things because they add to the price quite significantly. If you wanted a sub 9kg aluminjium disc brake bike you’d probably need nearer 1.5 grand to start seeing options.

As for alumiunium vs steel, in the price range you are talking about steel bikes tend to be a little heavier than aluminium though maybe not in all cases as the Boardman seems to demonstrate. Personally my next bikes will be aluminium rather than steel or carbon.
Steel might be considered the strongest material and more comfortable but I have a steel MTB and I just detest it. That said it weighs around 15.5kg!
Generally I find aluminium to be perfectly ok in terms of comfort.

+1 on material is way less important than build. You get fantastic riding alu bikes, and sh*t riding steel and vice-versa. However, I haven't yet ridden a sh*t riding carbon bike (but admittedly I don't think I've ever ridden a 'budget' model carbon bike).

Ride quality is not strongly correlated with frame material.  The design of the frame and, as Bobbinogs says, tyres, have far more effect.  For commuting, I would look for something that can take 28s with proper, full mudguards and possibly a rack, to avoid shitty shorts in the rain and a sweaty back in the sun.  I would be put off the Boardman due to its cable disc brakes.

Are you up for a self-build?  If so, take a look at the Kinesis T3.

A carbon fork won't do anything to help your arse, just ride 28mm tyres with the right pressure (don't be afraid to experiment).

Steel can be wonderfully compliant but you will struggle to get a decent steel bike at that price point. Stress not though, there are loads of other great options in the C2W bracket.