Dave
the understanding of wheel alignment aside from suspension and wheels / tyres is not generally good.
Even among car manufacturers, it is poor. For example Audi are practically incapable of producing a car that steers well. Lotus are among the best along with Porsche. Ford excelled themselves from the Focus onwards. Peugeot in the 205 era were also good. A Renault R26 is also good I understand.
I would say alignment services are like restaurants.
They will all adjust your wheel alignment, Caster, Camber, Tracking, on all 4 wheels. (there is a corner weight / ride height factor too but for simplicity we will ignore it).
Just as a restaurant will serve a meal from the menu.
But if you want a really good meal, there are restaurants and restaurants.
And for alignment, "Centre Gravity" is 5 Star. They understand: Grip, Feel, Balance, Your Driving style, the ARB's Bushes, everything about your car. Its not just a Set the Alignment Parameters into Manufacturers Tolerance exercise - ignoring the 50% tired ARB Bushes, and leaking damper, its a proper overhaul to leave you totally happy with the finished result. They speak to you.......
I'd guess Hartech do a similar thing, and thats why they quote £300 which is actually very reasonable IMO.
You get what you pay for, Horse-meat included.[

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good luck
George
944t