How to tag combined garages and studio

Some of the houses in the Kew Riverside development in London have two-storey buildings at the end of their gardens with a pair of garages on the ground floor and a space on their first floor that was marketed as a studio or working space. How are they best tagged?

Personally, I’d just leave the building as a garage, possibly (depending if the public are invited to the studio) with a node added for an office / gallery / ??? on level=1