Go on the UK chasers website, there are a couple on there. My friend keeps her horse at a yard called High Plains - near hexham, northumberland. it has got a really good xc course with lots of smaller fences. The website in on Uk chasers.
Yes High Plains is lovely and a really nice ride round too. For really nice tiny fences to start them off though I don't think you can beat Ivesley- but I doubt Pauline will let you go on it just yet as the land gets a bit boggy down the bottom end. I think they start letting you use it after the affialiated event there in April. Also the ride round Twizell Hall is worth a look too.
I like to take mine to Helen Bells, between Northallerton and Thisk. Great variety of fences of all different heights inc Water, ditches etc. Dont know if its open yet though