Adrian - yes I've got the SLX on one of my bikes. I haven't put it to much of a test but it's a nice, quality bit of kit, that's reassuringly solid and seems every bit as robust as XT so I'd definitely give it a go.
Muffinski - yes I think there are issues about compatibility - but I'm wracking my brains to remember what they are. I
think that road and MTB front mechs operate with different cable pulls (which you could get round if you have STIs with friction mode for the front). But it could be the other way round - or it might have nothing to do with cable pull. Ring
Condor (make them do some work for their money) - and then post the answer!
I don't know where you live in London, but I find that I rarely need to change gears so I'm sure bar ends would be perfectly feasible.