rednose,
If, say, the roles were reversed and the building company wanted to drive over your land for any reason, would you be happy to let them?
Not trying to be nasty, just playing 'Devil's Advocate'. Crucially, you have made no mention whatsoever as to how you ever came to be allowed (by the bc) to drive on their private road in the first place?
The fact is, you legally have no right to do so, not unless you at least have a (written) authorisation? I very much doubt you do? It sounds like the bc have allowed you out of the proverbial 'kindness of their hearts' to drive on their road.
You should also - urgently - contact your local highways authority to find out exactly where you 'stand'? Sounds like you and the bc don't have a great relationship, which, if true, you ought to try approaching them - politely - with a view to mending bridges because it also seems that you need them on your side more than the other way?