It will depend on the wording of the clauses in the vesting order from the Council to your uncle, so your solicitor will obtain a copy. Normally in practice the council will want to see a first time buyer or owner occupier purchase ( where they do not own another house). Best to seek clarification directly now from the council as restrictions may affect the market price. In turn a reduced market price should be entered for probate. CAT is only payable when you are beneficially entitled in occupation/possession, so if unusual restrictions apply, this in turn may serve to delay your payment of CAT.