Go for one with a downloadable memory. Paperwork can be done back home and you don't have to write every items details down. For easy use my preference would be a 2nd hand Seaward Supernova (plus or elite) or Kewtech kt77 (both same O/S but kt77 more compact). Very easy to use menu system where you don't need to remember any codes. The Megger 4xx range is another nice, easy to use unit. The Fluke 6500-2 is nice looking, has a great carry case but is not the easiest of units to operate. The menu system is, in my opinion, rubbish. I would steer clear of the Metrel Omega/Beta/SigmaPat models unless you are very good at remembering which code does what or enjoy spending ages scrolling through menus. The old Megger PAT4 is another that I would avoid. I'm not a fan of the old Robin units either.
Personally, I would go for a Seaward Supernova Plus or Elite. Very reliable units, does both 240 and 110, downloadable and very easy menu system. You can pick them up on a certain auction site for around ÂŁ60-100. Only two downsides. They are heavy and have a RS232 interface so can't plug direct into modern laptops/PCs. A USB to RS-232 interface is around ÂŁ5 and if you need the download software I can supply that free.