As far as class legal singlehanders go, you have a few choices:
Acat
F16
F17 (Nacra F17, previously known as the Inter 17 - not to be confused with a formula class)
Hobie 17
I also believe that some of the Hobie classes stipulate a minimum weight but do not stipulate that there must be two persons on board. Did I miss any?
Remember this is the UK, so there are more options. You also have the Shadow.
However, the best option would be a F16 (yes I have one), you can tune it a little more to your "fuller figure <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" /> ".
If you want to go for a sail sometime let me know (I'm based at Grafham) or another option would be to contact JohnP (member under that name here) and get him to arrange a Demo of the Stealth F16 at Datchet - he builds them).
Don't write off the Kite option, Cats are far easier to get going when learning to sail with the kite compared to the 700. Much less swimming as you have a more stable platform (oh and they are
just a little faster )
Your options in the UK are:
Shadow (but IMO not so good for the larger sailor)
F17 / Inter 17 (I had one of these before the F16, but there are not many around the UK)
F16 <img src="http://www.catsailor.com/forums/images/graemlins/laugh.gif" alt="" />
A Class
F16 and A class allow you to set the boat up more as you require and you can also spec a stiffer mast for more power.
Added advantage of the F16 is that you can sail 2 up by adding the jib.