If you are on a budget, I would certainly consider fitting Comline brake discs. I have fitted several sets now to different vehicles, and am very pleased with them with no subsequent brake issues.
Their discs are coated which prevents the unsightly premature rusting of the hub area of the disc, and require no preparation prior to fitting. The purchase cost is very reasonable, and my experience is that they bed in nicely, with a good pedal feel within a relatively short distance. They supply pads in the Comline name and also Allied Nippon. There is no difference in the quality of the two, just different brand names. They are UK company based in Luton, with an informative website. Unfortunately, they don't produce vented rears for the Omega so I have used ATE.
No doubt Comline wil be 'pooh poohed' by some who have not even experienced them; however, from my own personal experience, I cannot fault them, and have used them previously on several difference makes of vehicle.
But everyone has differing experiences of different vehicle components...