You can buy in the US and use in the UK but obviously you'll need a plug adaptor when you get back for the charger and make sure that if you go for a 3G/4G model it can take a sim card, I know that the 3G Verizon does not so avoid like the plague!
There is lots of good advice and info on here plus plenty of members all too willing to help with any problems.
Remember, search is your friend. If you can't find the answer you need and you post a question then give as much info as you can to help members help you i.e. iPad 1 or 2, iOS version and name of app if the problem is with a specific app........and please don't forget to read the rules http://www.ipadforums.net/forum-rules-help-info/2119-forum-rules-everybody-please-read.html
You can download the manual for your iPad here http://support.apple.com/manuals/ and in iBooks search for "iPad user guide for" and you will find free comprehensive manuals for both iOS 4 and 5.
If you have other Apple products or are interested in other Apple kit then why not join our sister forum too at http://www.appleforums.net/