Thanks for your replies, all have been helpful.
Mirage: Dd1 hasn't had any lessons, she sometimes gets to ride on her friend's 6 year old pony (not RS).
The reason for the interest in buying one was due to the cost of lessons though; I thought if we bought one and have someone who can teach her on her own horse this would work out a lot cheaper and obviously she could ride as often as she liked. Due to the stables being on camp- the cost, if not free will be negligible (still waiting to hear how much).
marge2: Your post really did make me wonder whether I am cut out for it! I intend to book myself in for some days at a local stables to get shown the basics of looking after them and will see how that goes. I live on the same street as the stables on camp though so I won't have far to go each morning at least.
marialuisa: the girl who may be up for sharing said she would like a Welsh B, it doesn't mean a thing to me! Do horsey people just tend to have a favourite type?
Countrysmiths: I suppose what I'm proposing is the opposite of the share you suggested, in that I'll be the owner without a clue and the sharer passes on her experience to me and teaches my dds. Thanks for the link, it's perfect for what I was looking for.
I have looked at loans but I don't see that anyone with a horse that they care about would be willing to loan to someone like me, although the sharer has said she would come to view any possibilities with me as she knows how to spot tricks that they use etc but I expect I'd have to buy rather than loan.
Cost-wise it's definitely do-able - there's just an awful lot more to think about than that though.