You get to rate your own ability and that should you see you in a heat sharing with others of the similar ability. When a few of us went for the first time, we were useless, but we were in the bottom heat and out of the way of anyone with working vision, two thumbs and cars that drove in a moderatley straight line.
As for the BRCA membership, you don't need it for this event. Unless of course Maritime Raceway are BRCA affiliated and you have been to 3 of their meetings already this year?
Get booked in, it's a cracking event.