Hi,
We don't have cellular, but I have often read many ques. and answers here just for my own info when we were first buying. I do know that in the past, Verizon had a different system than ATT and others. That could all have changed with LTE. I checked a couple of articles and found the following links which might help you. PLEASE NOTE these were published in March and May of 2012, so things might have changed with the new ipad 4. Also note that you can buy a cellular here without a contract that you could then set up with your own UK phone company.
http://www.tomshardware.com/news/Apple-iPad-UK-4G-LTE-Australia,15634.html May 15, 2012
http://apple.stackexchange.com/questions/43972/are-the-new-ipads-ipad-3-for-sale -in-the-us-unlocked-for-the-uk Mar. 2012
You also said you wanted retina display and then said you were probably staying with 02. If by that you mean the ipad 2, I want to let you know that the ipad 2 does NOT have the retina display. That would mean you'd have to get the old discontinued 'new' ipad or the ipad 4. And if I were you, I would not even think of buying an old 'new ipad, even if there's a great sale on them. I'd go straight to the ipad 4.
Make sure you do as much research as possible.
Hope this helps.