Im over in christchurch. So pretty damn near to you. I have tried PC World in christchurch and they have said that all their wii's have been taken for . I went into woolworths and the stupid chavvy girl behind the counter didnt seem to have a clue what a wii was, even though they had a wii poster and boxes in the store.
Other than that I reccomend trying john lewis, Il be trying the one in southampton, cant remember if theres one in bournemouth or not.
As last resorts you could always try places such as argos, littlewoods, smiths as well as tesco and other supermarkets.
If all else fails your pretty much guaranteed to get one in the next week or so, So dont be too grumpy if you dont get one. My friend preordered so il just play on his for a week