Hey feller.
Wow, thats a healthy list of, ermm...niggles!
Is it a pre/post facelift? I know there was some Omega 'C' switches on ebay a few days ago. If that helps? 
Ok, I'm splitting hairs here but:
Omega "A"...was the name of the Carlton in Europe
Omega "B"...is what we know as Omega's ('94>'03)
Omega "C"...no such beast.
Yeah, so they say. But some very prominent manufacturers still list then A,B and C. Plus my Gm brake pads had A Band C on the box. Genuine packaging. Strange.
I know what you're saying, but the "they" happen to be VX.
I've myself have seen cars for sale advertised as Omega "C", but officially there is no such model.
U.K EUROPE
CARLTON MK 3 - OMEGA A (1987 - 1993)
OMEGA - OMEGA B (1994 - 2003)
Yep. Not disagreeing at all. Just shows what "they" practice and preach imho. On the face of it A B C seems logical to me. I mean why call the carlton an omega A? And the face lift the same as pre face lift? But vx is as vx does, as Forest would say. A and B it is. Or B i should say.
Re the work list. My list started when the cam covers blew on my previous 99 omega. New seals and oil cooler re seal while there. But the oil damaged the leads and alternator. Really important to keep the breathers clear. Cam belt, wishbones, servicing, hbv, auto box fluid that enough without adding stuff on.
But rest assured, no cheaper car out there worth having. There really isn't.