Surefoot

Surefoot is expensive, but so worth it. I bought my first pair of ski boots from them in Verbier, where I was given a generous discount for being a resort worker. The service they offer is amazing, not only will they grind a footbed for your ski boots, they will then pad up your boots to fit your foot exactly. After you have skied on them for a couple of days, you can then take your boots back to have any niggling problems sorted out. Obviously this may be less relevant in London, but if you bought your boots in London, then had a problem in Courchevel, you can take your boots to be sorted out at the branch there, or anywhere else in the world for that matter. For anyone who takes their skiing seriously, this is the best place I can think of to buy boots.