Good evening v8s, I feel your pain.
Been there with one on my Elites that became extremely unruly to the point of being dangerous, and it took help above and beyond the call from members here to sort it.
First off appologies I'm extremely tired so may have missed a few facts among the posts here. I'll come back to it later but for now, some things I've found helped.
With any omega;
1 check the car fully for related faults and rectify.
2 set up
3 fit new tyres.
Those with Elites, esp those who like to crack on when driving, should strongly concider fitting firmer suspension. Elites are built for comfort so soft suspension is the order if the day. Trouble is soft suspension deflects the camber angle when compressed so tyres wear more rapidly with soft springs. So stage 1 Is a good time to fit something along the lines of Mv6 suspension.
Bushes are also key to handling but a trade off. Firmer the better for accuracy when driving, but there comes a point where ride quality and comfort suffers. However poly for the front wishbone front bush are accepted as giving an improved accurate drive with only minor trade off in comfort/harshness.
The 4 pots don't tend to destroy thier rear donut bushes like the v engines do but it's worth checking them non the less. Most seem to have at least slight rubber seperation sround the edges by now.
Once the structural stuff is sorted only then go on to the setup, but allow a few weeks for new suspension to settle to its new ride height first, if you do go down that road.
After thoughts, west country roads tend to roll and wallow an Elite quite nicely so try to stick to major roads where possible to keep the suspension from wearing the tyres. They like motorways. Difficult down there I know.
Never allow a set up firm away with the old "seized track rod" excuse. Wim went though a stage of this and it took 6 or 7 visits to get the steering straight.
There's a few guides on handling and set up so have a look through those. There's a thread on "approved tyres" so to speak. F1's being highly regarded so I do feel your problems lie elsewhere. Although primacy(?) and Michelins generally don't work too well once the profile is lost ime. I use conti sc3. Noisy but stable, good grip, just pray to the good lord himself that it never snows while they are fitted.
The nearest place I'd recommend to you is Micheldever tyres near the 303/m3 junction. They will remove track rods to free off and lube them. Avoid thier franchises though they a bit Micky ime.
Otherwise Wheels in motion franchises are much better regulated. Thier web site will guide you.
Steering idler should have zero vertical play. Put a foot on the front wheel and push it firmly for and aft. There should be no more than a couple of mm play in the wheel position.
Right I'm off to bed.
Best of luck with it. They do go straight, honest.
(but elites have the cards stacked against them more than any othe model in the omega range)