Oh I don't think it's general incompetence but most likely a lapse of concentration.
Well, I'm glad to report that, having just visited them, the car has had all its work finished and is just waiting on delivery of a new monobloc, before going into MB In Milton Keynes to have STAR codes read, all work verified, a 140 point check carried out and 3D wheel alignment done.
Hopefully I should have it back in 10 days from this weekend. Then it's just the transmission problem to fix.
Sat awaiting his new wheel.