I have the same problem, I noticed today coming back from canterbury to Hastings, the TC and ABS lights came on together for a few seconds, it did it probably 4 or 5 times and I think they came on just after I applied the brakes, I had a new battery about 6 months ago, but todays journey of about 50 miles each way is a rare longish journey for me, almost 100% of my Omega use is very short journeys of a couple of miles perhaps a few times a day, with blowers going and lights so the battery gets a lot of use.
I saw wheel sensor mentioned, a couple of weeks ago I replaced the rear brake pads for the MOT, the metal clips more or less disintergrated when i removed them and couldnt be refitted, could this be connected ? I also replaced a front tie rod and an advisory was front brake pads are low but I havnt changed them yet, just thought I would include this info
Just want to add that my old battery didnt make the TC and ABS lights come on so am I looking at a fubared ABS ECU ?