...Gillingham in Kent 43 x 16.5 ft? I wondered at a rough guess what it would be worth, the whole property is worth about 150,000, it is just for a bigger back garden for them with no building to go on it.
what i would suggest is getting an estimation by an estate agent, ask what it is worth with the land then without. After that add 5 grand and sell it to him. The reason for adding 5000 is because the cost will go up over time and you should get something out of doing it.