Some years ago the wifes car went in for a service at the local Ford emporium and they phoned to say it needed 2 new front tyres and the tracking checking. Tracking £75 to check and extra to adjust plus £100 for 2 unknown ditchfinders. The tyres were legal, it had passed its MOT while it was there so told them to leave it.

Next day went to Kwik Fit. They checked the tracking and as indicated by the tyres was out, £25 to adjust it. They suggested I had 2 new tyres since the ones on the car were badly worn on the inside edges so asked for a price. After a little price matching got 2 Pirellis and tracking for £140.

Highly delighted and after 3 more years the tyres did not scrub off so they did a decent job.

And regarding warranty how can having tracking adjusted by a non-Merc garage invalidate it, tracking is not covered under any warranty.

Just get it done.