Farmhouse private use

I have a client who is under investigation by HMRC. He has an Agricultural Holdings Act (AHA) tenancy on 180 acres with a house and buildings together with a farm business tenancy (FBT) on another 50 acres.

His AHA tenancy agreement states that he has to occupy the house and contribute to 50% of the repairs. The Inspector is arguing there is a private element to the rent and the repairs and he has now referred the matter to the District Valuer.

The rent for the AHA tenancy is around £45 per acre. The rent for the FBT is around £60 per acre.

I have spoken to the Tenant Farmers Association which says that around 70% of the house rent should be classed as private.

Does anyone have any experience of this matter? It seems unfair that an agricultural employee can occupy a house necessary for his employment...