Fire Protection Uk

Part of the regs is that the walls in the corridor (exit) must give 30 minutes to escape the fire (take 30 minutes before they burn). No new walls should be built or do they need to be doubled. If so with what and is it very expensivea

The building regs state does now under the control of the spread of fire or B2/3/4 D7E party in Scotland. The type of finish and thickness of food and the type of board is governed by the building ie. Is timber-framed, a block of flats, etc. direct link
As indicated by the remaining 12.5 mm is the base line, but it must be pink plaster board doubled Fire evacuation routes, and you cover all bases for a thickness of 15mm. If flats and timbered, and the double you need to double edge of each side with a vapor barrier.

All brick and block walls are constructed proof fire to a certain period of time, after a building caught fire, you will usually see the walls remained standing.

paint the whole place with fire-retardant paint

If the plasterboard thickness is 12.5, so that is what is required to give 30 minutes protection against fire .. it must be skimmed

if its plasterboarded then it must be 12.5 mm thick with a plaster skim. You can screw the drywall directly onto the wall, pick up the wooden poles (assuming the turn one wall + plaster) then skimmed, the only real expense is to get a plasterer. In so doing, as opposed to building new walls would save much time, effort and mess!