I'd go for a 14.2, any build. Your weight wouldn't be an issue at all and height wise really you could ride anything but may be over horsed with anything above 15hh.
You can ride anything you like being so light! Do any of your friends have ponies/horses of different sizes you could try? What size have you ridden up to now? It really is just personal preference. Also, different sized horses/ponies often feel larger or smaller when you're up there - mine and my OH horses are both 16hh - mine feels like a big pony, OH feels like a massive horse!!
If I were you I prob wouldn't go about 14.2hh - you have a fantastic selection of native ponies of that size who are capable of working up to a very good level, or being a friend to hack with depending on what you would like to do. What sort of things would you like to do with your horse/pony? If you would like to affiliate at anything then it might be worth checking the rules for over 16s on 14.2s - I'm not sure of them tbh but if you want to compete then best make sure that you can, even if you need to register your pony as a horse!
Your the same size as me, I'm 17 and compete BS but have my pony registered as a horse.
My pony is 14.2 and very fine and I feel perfect on him. Anything bigger I feel a little over horsed.
I also ride anything 11.2 upwards quite happily but if I didn't want to compete my desired size of horse would be 13.2.
What do you plan on doing with your chosen horse, Size realy only matters if you will be under horsed for eventing or if you lack confidence on a larger horse, My 9 year old daughter rides a 13.2 at pony club but was over the moon when she spent a day riding her aunts 16 pluss race horse, We have just got her a New Forest that should mature to 13-3 as she just enjoys plodding around and Foresters make great easy to do Ponies with quite a lot of potential if you want to progress later on....