I weight about the same as you, and one inch taller and I feel comfortable on 13.2HH's. Any pony of that height is strong enough, and I feel comfortable. My OH cometes shwoing exmoors and he won best Exmoor last year on an 11.2HH. They are fine showing, but for competition and jumping id say 13.2HH
Depends whether you are going for a chunky native type or more of a fine showy type. A 13.2 Exmoor or a Fell could easily carry someone of this height and weight.
Native ponies are strong, surefooted and hardy and can carry quite a bit of weight.