Cyclocross as my roadbike

Agree on the chainset. I bought a cheap CX chainset for the trainer and it maxes out about 28mph with a 12, so not a big deal. If that's not good enough then just buy a 50t compact chainring and swap it in, no drama.

Tyres... 28 spot on for towpaths but I find them draggy on road and go for 25 and take a small hit on the tow paths. I did have a pair of 28s Scwalbe Ultremos with race guard I think from Planet X and they were only marginally slower, I tries four sets before going back to 25mm gatorskins on this CX bike but anything 28/32 that was 'toury' I just hated on the road, like pedalling treacle. If you expect to ride full tilt on a tow path 28 is probably going to mean a lot less punctures, bit otherwise 25 will be ok if you are not HUGE and HEAVY.

Fit mudguards - less crap on you and the bike, less maintenance, less faff.

Personally I'd fit 28s and as for the chainset, just keep it or if you really find yourself spinning out then fit a 48 or 50T outer ring. FWIW I ride a 1x9 with a 36T ring and 11-28 cassette. I start running out of gears in the mid 20s but for commuting where my average speed is about 16mph, its not a problem.

CX chainset is typically 46/36 - you don't need such a big chainring as you're rarely going that fast and the smaller difference in size between chainrings means you're less likely to drop the chain

What is a 'cyclocross chainset'?

I'm running a Boardman CX Team basically as an all-purpose road bike for commuting, touring and general road duties. Keep an eye on road.cc in the coming little while for a review of the new Kinesis disc-specific cross wheels (http://www.kinesisbikes.co.uk/we-have-wheels/) which are, on the face of it, something of a bargain.

otherwise, a little further up the price scale, I'm quite keen to try the Stan's Alpha Disc wheel set (£450 on wiggle) which are really light for the money.

I wouldn't bother changing the chainset, just run the smaller sprockets on the cassette.

As for tyres 700x28 might be a better choice, lower PSI, plusher ride. I found Gatorskins a bit vulnerable to punctures, Vittoria Randonneurs have a deeper tread that I've found pretty much unbeatable for general duty.

Are you going to put mudguards on it?