just looked at the last message Daz sent me a few months back (re. bike racing). His last words were this:

You would be fine with the cat 3/4 lot. Only thing you will find is some of them cannot handle a bike. Skills can be terrible in cat 4 races.
Hey well done on the big miles. Enter some races before you're too old to regret it

I've just entered one Daz, cheers mate.