ah, here we are again, very common problem on the omega unfortunately, well not so much a problem as unknowing garages not knowing or caring that the omega shocks are adjustable for camber.
Usual approach applies, rectify any suspension faults, full geometric set up at wheels in motion or the like, THEN fit new tyres.
Problem is your set up is now so far out the tyres will be ireperably worn causing handeling issues until they are replaced. Its possible to replicate the old camber settings by measuring the wheel rim to shock distance prior to dismantling. Or set the camber to a tad short of vertical with a spirit level on level ground, purely to minimise tyre wear. Then drive the car to a set up company.
Max camber if the shocks are just bolted up can approach something like minus 3 degrees. Enough for the tyre sidewall to rub the shock body and destroy a tyre to the wire in 3k.
Best camber setting is WIM's recommended -1°10 minutes. Merely setting up to "in the green" "as factory settings" can give similar poor results, as the tollerances from vx are far too wide.
hth.