I have read on this forum a number of descriptions of the gears in the throttle body stripping and what that sounded like and various other signs and symptoms.

About two weeks ago when I shut the engine down there was a fairly low volume squeal and grinding noise that went on for a few seconds during and after engine shut down but nothing that really alarmed me. I started up again - nothing unusual to be heard from driver seat anyway. Shut down again and again I could hear nothing unusual.
Over the next two weeks no more strange noises but it felt just a litle different on shut down - slightly protracted, slightly rougher but I wasn't at all sure that I wasn't imagining it.

Had the car serviced Friday and mentioned the experience and queried whether it might be the dreaded throttle body failure. They looked at it, and got a read out that confirmed this was the case. With the bonnet up and engine running there was actually a rattling noise coming from the TB but that wasn't obvious with bonnet down and certainly not from the driver seat.

I suppose that I am writing this experience up as on reflection the noise made as the unit failed was brief, one off and not especially loud or alarming and the only clue that I had afterwards that something might be amiss was a fairly subtle change in the way the engine shut down such that I had started to convince myself that I was imagining it. The difference is blindingly obvious since replacement I have to say with the whole shut down being instant and totally smooth but the rougher slightly longer shut down was hardly anything to set your pulse racing with anxiety!!

I had thought from other peoples experiences that it would all be rather more obvious than it was.