The way I read it is I can tow anything UPTO the cars max weight limit, since an Omega + the Omegas weight is less than 3.5 ton!
If towing over 750kgs, the trailer MUST be braked.
But the whole towing law is a big grey area, nobody knows for sure!
Cant give an example at the moment as im at work and cant really stay on OOF for too long! So will try and explain better later on! 
EDIT: Im 21 by the way, so only had my licence a few years! 
You can tow a trailer over 750 Kg as long as its MAM is less than an Omega's unladen weight (approx 1600-1750Kg) and the MAM of the Omega (2200 Kg ish at a guess) plus the MAM or the trailer does not exceed 3500Kg. So, you are looking at a trailer or MAM up to about 3500-2200 = 1300 Kg, which must be braked as you say.
Note that's the MAM of the trailer, so if you were to tow an empty trailer weighing perhaps 500 Kg that has a MAM of 1500 Kg you would still be breaking the law.
Mad, I know, but that's how beaurocrats work create work for themselves.
Kevin
Thats Correct Kevin, Beat me to it! Must admit though, I didnt think the MAM for the Omega was that high, but then again ive never looked into that!
