Which skiff to choose

Depending on your experience, the 800 might be ok. I got one a year ago and have since taught my girlfriend to sail on it (from scratch) in twin trapeze mode. We've done a bit of swimming, but not much. We haven't been out in a real blow yet, because we've not had the opportunity, but we're coping fine in a medium breeze.

I had no real helming-from-the-wire experience, and sailed the RS300 previously.

DONT DO IT!!!!!!!!!!!!!! the 500 is so slow compared to other boats with a wire upwind. and if you can get around that its realy not much bigger than a 29er. i tried the one at Burgfield and it felt a bit odd on the helm, not light but not heavy just odd. it will be an easy boat to learn in but you will want to get out of it and into something racier quite quickly.

I'd say an RS4000 or Laser 4000 are you two best options (assuming you have decided to go down the asymmetric route) - both will happily carry your weight. The 400 is inherently a bit easy to sail (no trapeze to worry about, smaller kite), but both are fast enough to be exciting, whilst not being too hard to sail.

Second-hand prices are fairly low at the moment, so lots of bargains about. Also both have excellent UK series if you want to do some proper racing.

Boss/5000 might be a bit much (and are dead classes), 59er is a good boat, but no class racing to speak of, Buzz, 29er and 800 are probably all too small.

B14 could be an option, but could be a bit daunting for a new-ish crew - a long way from one side to the other (through quite a small gap), and a big kite to pack into a small bag, instead of an easy chute drop.

Good luck!