It will depend on whether you want a group or individual lesson, your location and the riding school you go to. Around Windsor I've been paying £20/£30 for a half hour private lesson, which is why I don't go very much at the moment. Once I have more time to ride I will go more often, but a lesson at that price for once every 3 months or so with no other riding in between isn't worth it for me at the moment. Come on lottery numbers...........