Update. Sent though all invoices.Sent him JIB approved gold card, ECS registration. Regulations that are to be met in Northern Ireland etc. Final demand with payment due this week. He emailed me a copy of an email from the local council building control stating electricians have to be registered , again not who with, to sign off works. Phoned them and it turns out it’s a fraudulent email made up by the home owner. So looks like it’s going to small claims but pretty sure I’ve all bases covered and he is trying to scare me off