They will work in terms of wifi, and with the AT&T version you could potentially swap in a UK micro-sim to use it on a UK 3G network - Verizon iPads are CDMA based and don't use sim cards, and there aren't any CDMA carriers in the UK (or, as far as I know, in Europe).
(For future info, typing all in capitals is considered shouting, and may mean that people are less likely to reply.)