ahh, depends where abouts you are
Evans stores of any size generally have a wide range. Take a trip into London on the train and there are lots of big shops...Evans e.g. Mortimer Street, Waterloo, Cyclesurgery e.g. Victoria, Spitalfields, Onyourbike (London Bridge), Condor if you're feeling rich
I went to the Cycleshow in Birmingham last year - it was pretty poor for actually seeing bikes that you may wish to buy