Turndial - so you are an Australian living in the North of England, You are asking what sort of horse of horse will suit you bearing in mind your height and weight,
Well, in a way that's the wrong question. The more relevant question is associated with what you want to do with it and how competent you are at riding.
An old fashioned Welsh Cob D say one of the stocky cobs bred for work. Height anything above 14H2 bred with a broad back and plenty of bone in the legs might well do. But the big question is whether you two, horse and rider, suit each other.
When you go to see the animal, mount up in a fenced arena and go round in circles at the walk . After 5 minutes or so, then ask yourself if you feel comfortable. Do you have a good feeling in your gut about the horse? If you think all is OK, arrange to go back two or three days later and this time take a knowledgeable riding friend with you. Mount up again, walk around. Let your friend watch.
Ask him of there is any reason why not to buy the horse.
If he says: 'No - its OK' then arrange for a vet to call and do a full examination.
If the vet gives the horse a good report then wait one more night - and go and buy the animal.
You have a 50/50 chance you made the right decision - either you did or you didn't buy the right horse. The problem is always that you won't know for six months. Be lucky.
Seriously consider going to a riding centre and ask if they have any heavy weight cobs for you to buy. Then ride the horse several times before you agree to buy it. Try riding it away from the yard on your own - if you get yourself and the horse back to the yard in one piece, then maybe it might be the horse for you.
Don't be in a hurry!!!!!!!!!