There have been lots of threads recently about problems with RCCBs tripping
out. The advice has been to isolate different parts of the house circuitry
to find out where the fault is. Where a fault is intermittent, but frequent
enough to be a nuisance, this is not really practicable.

How would a trade electrician find the fault? Presumably there is test
equipment? What is this, how much does it cost and where could I get it?

Peter Scott