Might be pushing your boundaries a bit but you can use The Links and the Cambridge polytrack on Newmarket Heath (both on Cambridge side of Newmarket!). I used them a couple of years ago and I cannot remember how much they are I'm afraid. Call Jockey Club Estates if you want more info.
the Grange Farm one is long gone now, i've been told. the one near Lynn is supposed to be good.
if you find one, please let me know where it is, as i'll need one at some point i hope!
Thanks everyone, Miller if you can find the number for the one between Pinchbeck and Spalding that would be great, as probably the closest!! I reckon if I took my boy on Newmarket heath he'd think he was a racer again as he was based there at Warren Place!! May have to consider the one at Kings Lynn if Spalding one doesn't exist anymore!! Thanks again