Going back to the questions….
As already said, you can’t go wrong with Megger 150x or newer or Fluke. For ages they have covered all the bases.
Metrel do a very good budget unit called mi 3125. Unusually for its price point it can do the 3 point earth testing that Mike mentioned, though this isn’t often needed for UK domestic work.
Kewtech Kt63 and newer are good, though you do have to move leads to different sockets for live and dead tests on some models. This eventually annoyed me to the point I sold my KT63.
If buying 2nd hand then get one that has just been calibrated.
There are usually a few Megger 155x and 150x units with calibration on eBay for about £250-£300.
Anything cheaper is a gamble really.
Automatic RCD tests are not so essential these days since the testing requirements have relaxed a little.
Some people like the ability to do 2 wire low current (non trip) loop test. This is not essential. My own view is that while it ticks a box being able to test at a light switch, the actual result can be very inaccurate and I prefer other methods.
If you want that feature you need later models E.g Megger 1721 or 1741.
Avoid Robin, Kyoritsu MFTs as these are now very old, some can’t null test leads, some don’t have 250v IR tests.
Feel free to post things you’ve wondered about buying. It’s a bit of a minefield at first!
