I have towed with a Petrol Omega 2.2 for 3 years, not a problem, even did the south of france last year, brilliant, only problem it's a little bit thirsty, you should be OK with diesel.
Dave, I tow a 1200kg unit with my 02plate Petrol Omega 2.2 Estate with ease. I've had it for 4 years now and the only problem I have is keeping to the 75kg noseweight.
As Paul says it can be thirsty and as I tow most weekends between May and Sept I find I need to keep a check on the tyres.
Friends keep trying to talk me into changing to a 4x4 but I like the omega it's a lovely car to drive solo and tow with.