Arn't there any near the whitehorse thingy in Wiltshire Tengu. (not the Uffington one) As far as I know Juniper likes chalk, but maybe not exclusively.
There's a few juniper bushes around the Chilterns which is chalk area, unless your whitehorse is on limestone.
I go walking around the Pulpit hillfort area sometimes (Chilterns) and will see what I can do next time I go, but it may not be for a while.