All my Omegas wore their front tyres on the inside edges, I reckon it's a consequence of the Mcpherson strut front suspension with rubber front horizontal pivots and rubber rear vertical pivots. System works well enough, is silent, and cheap. Replacing the front pivots with nylon stiffens that end, then replacing the rear pivots with nylon stiffens it so much the wishbones break.
It's obviously desirable to righten the front bushes in the middle of suspension travel so that the rubber flexes in both directions during service. This means tightening the bolts with the front of the car on its wheels, tricky.
un-even tyre wear is down to worn or badly adjusted suspension components Terry
(or incorrect tyre pressure)
I've never suffered un-even tyre wear in 20 years of big RWD vauxhall ownership carltons and now the omega
similarly with astra,cavalier,vectra B ,corsa and the zafiras ,all Mcpherson strut based
BUT, I don't let suspension components wear enough to be flagged as "slight play" at MOT time
(and MOT is "meets minimum requirements" to pass)
suspension parts are cheap,
even black and round tyres are expensive if they wear un-evenly and need replacing prematurely