not defending the shop at all but strictly speaking on the MOT test you are NOT allowed to carry out any repairs to the bike during the test especially on the new computerised system
however as a curtesy they should have done it for you
they shouldn’t have failed the exhaust if it was legally marked unless it has baffles removed or it’s leaking either
the no waiting room is a bit crap but again all the station has to supply is a viewing area
you can complian to the VOSA if you are unhappy with your test results