I believe so but permission should be sought from the land owner and I think private land to which the public has access is still covered by highways law eg beaches.
You could try your County Police Traffic Department to check.
You could also try this for young driver groups...
Siamsal is right. But even where the Road Traffic Acts do not apply, it is still worth trying to get insurance. If an accident happened and someone was injured, the compensation could run into many thousands of pounds.