hey
erm i was riding for about 4-5 years before i loaned my 1st horse, and it is still very expensive. So even though you dont have full ownership of the horse it is still expensive.
You sound like a great rider, but its not only riding you have to be good at before you have a horse. There is all the stable management, like tacking up, grooming, mucking out etc etc.
There are loads of horses or ponies up for loan, not only at riding schools but alot of people privately loan out horses, so that would be worth checking out!
I loaned a pony/horse and it was such a fantastic experience!
But make sure you are getting the right sort of share of the horse hat you are paying for. Make sure you dont pay too much for what you are actually getting!
Loaning or sharing is also a great way to make sure that if you did eventually buy a horse, that you would want to!
Whatever you decide to do, have fun!
I think this site is pretty good, check it out!
Good luck =D
http://www.horsesharesuk.co.uk/pages/page/11/