Now now boys, less of the domestic!
I'm going to stick my nose in probably where its not wanted but heres my take on the situation. If you want to claim the most powerful in the UK you need to provide documented proof otherwise when someone comes along with a figure larger they will never know if they are running more donkeys and the record gets lost in secrecy.
Ultimatly horsepower is pub talk, but its great pub talk
I have no doubts it does hold the record, you should be proud to show the world your achievments.