Thanks for the replies, from what I can find online it agrees with what you've all said. The work included adding an electric shower and a whirlpool bath (so from what I can find
online) I should have got a certificate.
I assume the builder should have informed me of this and included it in the quote before I started asking about it.
If the electrician he used is not registered (which I am assuming otherwise he should have no issues getting the certificate) and the work was finished more than 5 days ago what is the next step? I havn't finished paying him yet, but it seems he wants me to pay for this certificate that I now need (Homebase 2 year warranty is useless without this). As it is a regulation that he should know about I assume that my current stance that I want the certificate, but do not see why I should pay more is justified. (If he had at any point said I needed this certificate and added cost to the job that would have been fine, but as I only find out about this now after the job I can't help feeling that he's trying to get away with a 'cheap' job / abusing the fact that I didn't / don't know about these things)