LOST Complete Season 1-6 Box Set (DVD) is £55 at Tesco just now but use the 15% discount code (thanks to millarcat) and it brings it down to £46.75 delivered. It's a first time user code so if you're already registered then you'll have to use another email address. Next cheapest is £60 at Zavvi, Amazon is £97. Not a bad price for anyone who hasn't seen it and not fussed for blu ray.
PLEASE NOTE this is the DVD set and NOT blu ray - but then you probably worked that out for yourself anyway, considering the price and that the blu ray sets are around £170..