I've done over 70 of these repairs now. Yep, have nightmares about them
Based in Midlands UK and if you google "Secure Vehicle Against Rolling" or my user name with spaces in, you'll find me.
I always change the spring (I've had units in which have the unwound spring which have failed). Takes about 2-2.5 hours depending on the vehicle and there is a Costa and Wetherspoons up the road for you to relax in whilst I do the hard work. All with a 12-month warranty and you can pay cash, card, bank transfer. I've even dealt with warranty companies - just hope I can save some more people paying the extortionate prices asked for by dealers.
In my experience the dealers don't want the cars in the workshops. They can do 4 services in the time it takes to replace the gearshift and the techs just don't want to do jobs like this. Simple as that. My customers have been quoted anything from £1100 to £2500 and people have travelled from as far as Kent to take advantage of the repair service.