In reply to GunnyGuy:
A lot of Polar/cold weather XC gear I've found pretty hard to get hold of. Particular things like expedition quality synthetic -30 sleeping bags, lightweight snow boots, XC skis etc I've had to order from abroad. It's not that you can't get anything in the UK, it's just the range is so tiny that if it's not quite what you want you have to look overseas. It's compounded by the fact that companies like Sorel and TNF have regional sales deals in place that mean most retailers will refuse to ship those brands to the UK.
Also freeze dried food. As far as I known there aren't any companies in the UK that sell bulk freeze dried foods that you could use to make your own recipes. I've seen a few companies in the US but none here.