VAT conundrum – Mixed Residential Commercial Development

My VAT conundrum is –

I am looking to purchase a group of buildings freehold. There are 4 buildings in total, split into 10 separate units.

Building 1 is 2 units both let out to 1 tenant with a 10 year lease.

Building 2 is 3 units, unit 1 is let to a tenant with a 10 year lease.

Units 2 + 3 are vacant

Building 3 is 3 units, unit 1 is let to a tenant with a 3 year lease

Units 2 + 3 are vacant.

Building 4 has been sold on a 999 year peppercorn lease.

There is parking for the tenants on the land.

I want to buy the buildings and land as a going concern thereby removing the need to pay VAT. I would be keeping the tenants but converting the vacant units to residential as there is already Permitted Development granted on the whole site.

Would my converting the empty units effect the VAT situation when buying as a going concern?

Form 1614D could perhaps be used converting office to residential but part of the development would not be possible for a few years so this may effect the use of the form.

What would be your advise in this situation?

Thanks

Clive