Topic: VAT on Refurbishment to Residential Property

We are looking to start the refurbishment works on a house that will become our main residence.
The property has not been lived in since September 2015 when the previous owner moved into a home.
We bought the property in April 2016.
We can prove from the electricity and water readings that the property was uninhabited from September 2015.
Is this sufficient proof for HMRC that the property has been unoccupied for at least 2 years?
We want to be charged at the lower rate of 5% on the grounds that the property has been unoccupied for 2 years.
Can we proceed on this basis?
If so - should we instruct contractors to charge us at the 5% rate, or do we get charged at 20% and claim back from HMRC?

Thanks.