Hi Jazb
The DIY Housebuilders Scheme allows you to reclaim some of the VAT that you have paid out for your project if you are converting a non-residential building into a new dwelling ie a qualifying conversion. You can check para 7 here https://www.gov.uk/guidance/buildings-and-construction-vat-notice-708
However, this is a complicated area and my suggestion is to find a local VAT expert who will look through the paperwork and check all is robust before thinking of getting a reduced rate on the conversion.
Regards