As others have said, no Omega 2.2DTi auto.
The only Omega DTi auto available is the 2.5DTi, but that was never offered by Vauxhall, only Opel, and is only available in LHD, but does have the 5 speed auto.
I have viewed 2 2.5DTI Autos....iirc it is the BMW engine, same as in Rover 75.....
As for price, £1600 is way of the scale, a 2.5CDX for sale locally for around £800, been for sale for so long I recon a good discount on that price.....
the Rover 75 Diesel has the E46 Non common rail 2.0 Diesel 134bhp engine 4 Cylinder
The omega is cursed with one of BMWs worst creations the M51 Diesel 6 Cylinder
Whats wrong with the M51?
Nothing once retuned back to BMW spec. Ok, it's not a modern engine, so cannot match the newer common rail similar sized units, but it's not bad. Generally reliable, but when it restricts, it's normally spectacular!