At this point i've decided to just wait it out until I can sort out for a proper PT rather than spend 1k now and 2.5k later to upgrade, having trouble finding a sparky that will actually show up on an appointment or reply after they're on site.
I do have an isolator on the garage electrics and the breaker is actuall type B not A, so it should hold to surges 3-5x rated current (48-80 amps). So there might be an option to upgrade just the isolater and add an 16amp plug.
16A has been fitted for a reason (which may be just ‘cos that’s the default). Without knowing the cable type and the way it’s been run (eg through the middle of a load of insulation) it may not be a good idea to change it. You won't need to if you just fit a 16A socket. (NOT Plug!!) See 16A 230V Surface Interlocked Socket 2P+E IP44