part p

hi guys I would like some advice please.I recently purchased a house and wanted the power cable moved obviously the cables had to be extended.I had several electricians in to give quotes etc around 1 1/2 to 2 days work but none of them could fit it in with their schedules all were busy.I ended up having someone who quoted four days work had to be completed by the time the power co came some three weeks away. this chap to cut a long story short did not complete his brief spent most of his time out of the house.when it came to his bill asked that it be reduced on the grounds that he failed to complete his brief and that he spent very little time at the property.I had to get some one else in to do finish the work. whilst he was there I replaced a lot of the old sockets with smart ones same with light switches.he now is threatening to report me under the part p of the regs. my question is. I was under the impression that as long as u did not go into the consumer unit u could replace sockets and switches is this so or is it illegal. tia liz