If the test gear is unreasonably expensive I will chat to our local
electrician about commissioning the wiring.

To do it properly, you need a continuity tester capable of 200mA test
current (NOT a multimeter!), an insulation resistance checker capable of
500VDC, an earth loop impedence tester and an RCD tester. You can get the
whole lot for around 600 quid. Of course, most people don't seem to do it
properly.

The most important part is the continuity/insulation resistance tester,
which are normally on the same instrument. The cheapest of these are around
200 quid new. I got mine for 35 quid on eBay from someone who thought it was
a broken electronic thermometer. He admitted afterwards that he sold it
because it gave him a nasty electric shock when he was playing with it.
(500V does that!)

Christian.