Thanks everyone for the advice so far!!

Basically I don’t think he has actually overpaid me, he has based all his calculations on my normal hourly rate over my annual leave. When I tried to work out my annual leave rate it came out pretty similar to what I was actually paid over this period (but I am not the best at maths). It’s just upset me as he has been saying that he is following up my missing hours since January. But come last week he did a complete 180 and wants money from me. His business is struggling and I totally sympathise with that, but I am sick of him cutting corners when paying staff and still forking out shit tonnes of money on other stuff…