I'll bring the tinny Hardie,all 3.5m & 5hp of it

Hell I'll even get a RESCUE sticker for it.

I think you will find you have to join WWA 24 hrs+ before the race to be covered by insurance. If something goes terribly wrong WWA dont want to be in potential trouble either.(or me)
Actually years ago i had to get my TTL3 boating ticket so I was covered by the Yacht Clubs insurance doing rescue work.Its all about covering your nether region.