Just one thought – who signed the lease, the executor, or the late grandmother? If the grandmother’s signature is on it then perhaps that’s your offence – the impersonation of a deceased person (which I think is a criminal offence, but not sure).
Another thought – did the grandmother die intestate and if not who inherited the house? Was it left in trust for the deceased’s granddaughter and therefore you would need to consider whether she is the beneficiary of that trust. I would say yes if that was the case so benefit wouldn’t be payable under the old Reg 7 (1) (e) for the dates you mention. You could resolve that by asking for a copy of the grandmother’s will. I must say that I ask myself one pertinent question – why didn’t the executors transfer the property over to the beneficiary of the will ?
Hope my ramblings are helpful.
Do I know what I'm doing? The jury's out on that........................