Currently a couple of oil rads in the (well insulated) office, and for the fitting bay I just use a gas space heater when required , not ideal I guess but I have noticed that any moisture just condensates on the cold shutter doors so no biggy!
My intention is to put in an air source heating / cooling system, a self contained twin output set-up looked to be around £1200 and would heat or cool the two areas independently, would fit myself.
something like these.. https://www.appliancesdirect.co.uk/p/ei … gICx_D_BwE