Which boat do I buy

Sorry to be a broken record. But if there is a fleet of any singlehanders at your club then assuming that you dont fall outside the typical weight/height range too much then just get whats at your club. Given your height and weight most dinghies will be fine for you but perhaps stay away from Finns and Phantoms unless you plan on eating a lot of pies!

If there is any choice at your club, eg. RS300, Laser, Blaze etc. then ask for a go and make your mind up based on that.

The only reason to go for something that isnt at your club, is if there are no established classes to race against or if you are just someone who likes to have something different and not be part of the crowd.

Not on the list, but the best value - the RS600. Mind, you'll need safety boat cover for that, and for the 300, I'd say.

I think we need to know what your current sailing experience is.

The 300 is a delightful boat, but very advanced. In its early days a lot of people bought them and failed to develop the required skills which gave it a reputation of being too difficult to sail. You'll certainly need steer for balance skills and other high end techniques to succeed in one. I don't know I'd really describe it as being any easier to sail than the 600.

If a Laser sounds OK to you then it has some big advantages in that you can buy and sell easily and get coaching, and if its a step up on what you sail at the moment then its also a good stepping stone to the more challenging stuff.

The Vareo and the RS100 are both quite specialised boats. They're really in the same sort of performance area as a Laser, but with a kite attached. That may or may not be something you want to do. Personally I dislike sailing singlehanders with kites because I always feel compromised by lack of hands: it always seems to me that I could sail it much better with a third arm, which is frustrating, so, again speaking personally, I only like kites on two handed boats. But clearly other folk feel differently.

Sorry yes, 

Sorry i didn't phrase that well enough.