A couple of quick things for the OP.

The shop/seller has to participate in the Bike2Work scheme.

I would really look at Whyte Bikes (British company). I test rode a few and really like their fitting for the British roads. Get the optional mud guards thrown in as well (for free) when you buy it.

I like the idea of a 1x9 or 1x10 set-up (only a rear mech with no need for a front one) as Britain seems quite flat compared to my time in Germany. I really like the idea of hydraulic disks for the wet weather ... it's here already I rode some cable disc-equipped biked from other companies with Avid BB5 ad BB7 and was not impressed at all.

I like the Whitechapel but a Shoreditch is always very nice.

Whitechapel, £550 | Whyte Bikes
Shoreditch, £650 | Whyte Bikes

I haven't encounter much terrain in the UK that would require more than the 1x9 drivetrain on the first bike.