I took my Vauxhall to a main dealer to keep the full service history up.
I was told it was leaking coolant, a drive shaft gator was split and it was leaking oil, and quoted a silly figure for repairing it.
I also asked them to look into juddering brakes (suspected front left disc was warped, but wanted to know for sure before ordering one), and they said all the callipers needed re-building or replacing!
My dads an old school mechanic (retired now), so I bought the new drive shaft gator and we set about fixing the problems.
No oil or coolant leak visible at all, and the old gator just had brand new white grease smeared on it, no splits or holes, it looked new.
6 months later the oil and coolant level didn’t change (oil went down a tiny bit as you would expect), still no leaks visible and no more grease around the gator.
Replaced the disc too and it cured the brake issue and it stayed cured for over 6 months until I sold the car.
I may be paranoid, but I’m sure they “find” stuff wrong on old cars to sell you a new car – the dealer phoned me up every week for a few months with “we notice your car has some issues, we can guarantee you can run a brand new corsa for less per month!”.
Use independents now.