magsmay,there is one plus. The old farmer's estate pays no inheritance tax on the farmhouse when he dies, so the son gets it free of tax, just as he does the rest of the farm.It gets 100 per cent relief. Don't quite get why your barn conversion wasn't allowed as a farmhouse. The planners have an inbuilt objection to barn conversions on green belt. They may have thought that, since you were farming from a house 4 miles away, there was no need for you to have house as an exception to their rule; there was no farmhouse needed on site to run the business from. Holiday cottage ? That may get by under local rules to encourage tourism, as holiday lets. Two month's let probably keeps the owners onside. As usual, you need a good team of agents, who have close contact with planners,or of course, the name of a local builder whose previous work is contrary to policy (It's amazing how he'll achieve permission impossible for you, through some mysterious means)