Unfortunately, access over an unadopted lane is not a planning matter and is a civil issue between the interested parties. Notwithstanding this, if the lane is not within the applicants ownership, which from the sounds of it, it is not. Then they should have signed the appropriate ownership certificates and served notice upon the land owner. If there is no land owner, or the land owner is unknown, an advertisement should have been placed in the local paper. The red line boundary should edge the site and also include the access arrangements up to the adopted highway.
You may need to take legal advice from a solicitor who deals in civil law.
