Yes thanks this helps a lot, now I just need to know which type of
meter to buy, is this one suitable:

http://www.screwfix.com/app/sfd/cat/...00153&id=14469

Although this will give you an indication of the connection, it isn't
actually good enough for the regs. You'd need something more like:

http://www.tlc-direct.co.uk/Products/TM9054.html

These meters will apply up to 200mA to give a much more reliable indication
of resistance and will give 2 decimal places of ohms. Obviously, this isn't
the sort of price range you're looking for to test one circuit. To fully
test a circuit, you need one of these (which also does high voltage leakage
testing) an earth loop impedence tester and an RCD tester.

I wouldn't be surprised if you can hire from HSS, or you can just use a
multimeter and hope, but you won't have complied with the regulations. Last
I looked, the going rate on eBay was 50-100 for each digital meter.

Christian.