Thanks for your reply.
As you do not have a right of access or right of way, your hands are very much tied, I'm afraid.
Even though you have been using the access for 15 years, this does not give you any legal rights over the lane (to gain such a right, you have to show that you have had unrestricted use of the lane for 20 years or more).
Although this third party may indeed not own the lane (you would need to instruct a local Solicitor to check this, via the Land Registry), sadly you have no legal standing to take any action against him, on the basis that you, yourself do not have any legal rights over the lane. (If you had a right of way/access, you could indeed take him to Court with a view to obtaining an Injunction to stop him preventing access).
I appreciate you are not going to be happy with my answer, but the best you can do is to rely on the Council and hope they do take enforcement action against him for breach of planning legislation.
I am sorry this is not th eanswer you were looking for, but it set sout the legal position.