I just found out today that Zavvi at the Glasgow Fort got in 30 wii fits. They don't expect them to be there for long, they sell out pretty quickly.
I've had a look at other sites. On amazon the minimum price is £85 and on game they only seem to come with other packs, ie wii fit family, wii fit ski. Zavvi, as far as I'm aware, are selling them at rrp but I'm fairly sure it's one unit per customer.
Anyway if anyone is interested I'll try to keep this updated because a lot of folk are wanting them for christmas.