Coconut Powder is sold in Tesco, I use it for fish cakes or sometimes meatballs, it stick the product together.
Blue Dragon also make it, but its very difficult to find.
Thai shops also sell it a lot.

That is most likely Coconut Milk Powder and not the flour. I have never seen the flour in my local Tesco and it stock a huge variety if 'world foods'. The Blue Dragon is definitely milk powder.

In response to Axe: Blue Dragon provide both "Coconut Milk Powder" and "Coconut Powder" as part of their range, so I'm not sure whether both are the same (?). I've not seen any "Coconut Powder" at two of West Yorkshire's top Asian Supermarkets  and wholesalers. I've seen plenty of coconut flour in large pack sizes, so I can only assume that BIR's use it (the flour) in bulk.