After searching around for a Wii Fit board online I discovered they have become like gold dust over the Christmas holidays (all the big online retailers are sold out).
So I went to my local store for shopping (Asda Ardrossan, Ayrshire) and noticed that they had the game & the board for £69 - £9 cheaper than the cheapest retailer online (Carphone Warehouse)
You may have to ask at customer services for the board, as this store had none on display!
Unfortunately, I have no idea how long it will be at this price for, or if this is their normal price. Either war it's cheap