Hi Dan Rhodes,
The main condition for treating VAT as input tax is that the VAT incurred is in the course of the business and is in relation to the making of taxable supplies.
An option to tax on a property results in taxable supplies being made in connection with the property and so would then allow VAT on purchases to be treated as input tax.
However if you as the tenant are using the property as an office for example from which you are running your business and making taxable supplies then you can recover VAT as input tax in relation to the property.
Please see condions again for the recover of input tax:
10. Introduction to input tax
Thank you.