Could the land be considered to be part of an Agricultural Holding?
If not, part D, of the 'Ownership Certificate' accompanying any Planning Application (the Council can make and approve its own applications) ought to cover them........
http://www.hounslow.gov.uk/own1_040826-2.pdf
Naturally, they will have to hand it back to the owner, should s/he ever make him/herself known, and remove any structures, etc. which they have installed, should the owner require........



