The air bag was standard in the UK. I think if it's simply disconnected the SRS light will come on and that will probably result in a MOT failure. However the MGOC sells an aftermarket Momo wheel that required the airbag to be removed - I guess the SRS needs to be reprogrammed so that the light does not come on (you may just get away with removing the bulb but a thorough tester would probably check that it illuminates then goes out. Here is some stuff from the government on what's checked in the test:
2.6 Seatbelts
The vehicle will be inspected to check that:
the mandatory seatbelts are in place
they are suitable for the vehicle
they are in a good condition
they work properly
they are attached securely
The malfunction indicator lamps (MILs) or dashboard warning lights will be checked for the:
air bags
seatbelt pretensioners (which remove the slack from a seatbelt in the event of a collision)
seatbelt load limiters (which release a small amount of belt when it’s too tight)
2.7 Seats
1.8i Mk2 Solar Red, 16 inch square spoke wheels, MGFMania hood with zip-in glass rear window, DRLs, Kmaps ECU, Pipercross panel air filter, MGOC Supersports back box & some cockpit bling