sram apex front mech

But the main thing to start with is to adjust the mech's position relative to the chainrings. It should be as low as possible without touching them, and in the same plane as the chainrings (not twisted), which might not be as easy to spot as one might think, since the front mechs are often a bit bendy, rather than rectangular.

I've got apex on my commuter and the front mech is a little temperamental, requiring quite precise adjustment to avoid what you've described. Rather than having to slog back to Evans all the time, spend 5 minutes reading how to set it up yourself, it's really not difficult. I would recommend fitting an inline adjuster in the gear cable, and with that and the two little screws on the mech, you should be able to get it running properly. That, of course, is assuming the mech hasn't been damaged (bent etc), in which case no amount of twiddling would fix it!

Not had a problem with the front mech. The mech may be faulty, but I'd try a different shop/mechanic/mech rather than mixing components.

I think Evans is the problem here. When set up correctly they work fine.

I don't think double tap shifters work with Shimano mechs.