O
Octopus
OK we will assume said electrician is self employed, irrespective of the possible dubious worth of installing an up-front RCD. No holiday pay, no sick pay, scheme fees, insurance, accountants, and so on. You have no idea of the costs involved, do you? How much rent are you charging your Tenant? Bet it's a hell of a lot more than £348 pcm, and your probably depriving someone of buying a first home to boot.
So you think £192 to fit an RCD in place of a main switch acceptable?
I don't