The pub is currently closed,
It has already seprate 3 Bed Flat, which I would like to keep.
The Pub its self, I want to convert into 2 office spaces.
As the pub is closed you can't even do a dodgy TOGC (for avoidance of doubt dodgy as you have no intention of running a pub).
Therefore you can either suffer the VAT hit on purchase, or you can register for VAT, opt to tax the property and charge VAT on the office lets. The residential flat would be exempt . Any subsequent sale of the office space would also attract VAT. On the upside of VAT registering, you would be able to recover all the VAT on the conversion costs relating to the pub space, any costs relating to the flat would remain irrecoverable.