Hunter is the name of the alignment machine that's used, and involves putting the car on a lift that allows the car to move backwards and forwards on it's own wheels.
Sensor plates are clipped to each wheel and the car is pushed backwards and forwards a couple of times, each of the plates using external lasers and communications to calculate all the angles, caster, camber, toe etc and these very quickly show on the screen.
I wouldn't trust any business that Halfords has a stake in ..... unbelievably bad in my opinion.
Try searching on "Hunter wheel alignment near me" ....
I used a company called Pro Tyre who are near me, but you normally have to ring and book a slot as the alignment bay seems very busy to me.
I think the check is free, but any toe adjustment starts costing.
I've found that any change to any suspension components will always result in a change in tracking, and I've always found that the Hunter will find considerable differences to any other alignment system ..... but it always gets it right iny experience, and with a front pair of average brand tyres costing around £150 these days, they need a good set up.