I sold the omega today for the princly sum of 400 quid.
Right being the caring soul I am, I told the buyer to keep in touch if there was a problem.
Lo and behold I got a call back about an hour and a bit ago...
The ignition key housing snapped thanks to 15 year old brittle plastic. The guy removed the blade with pliers and tried the spare key in the barrel.
The spare key it would appear was worn or something as I remember it took a fair bit of jiggling in the lock to get it to turn, I only ever used it once, when I bought the car and never really picked it up again. The other key never had any problems until now where the case has now broken :

Anyway, the spare key was used, and now the lock is spinning freely as IIRC, there is a safety mechanism which makes the lock freewheel to stop it being forcibly damaged.
I've just called him, and he says the car is at his local garage. I'd like to ask this,
When the lock freewheels does this now mean a new barrel, or will just sticking the correct key in the lock allow it to engage once again?
I've found a supplier of OEM key blanks and transponder units, and for the sake of 20 quid i've offered to have a set sent to him so he can get the keys cut and swap out the original transponders.
Naturally i'm a bit peeved that it's all happened to the new owner within hours of sale. :-/