a research fellow at Oxford University, hit a pothole in 2010 while commuting in her daily driver '97 Porsche 911 Targa. That caused underbody damage and an oil leak. So, she tried to get it fixed somewhere other than a Porsche Authorized dealer or mechanic. You know how that turned out.

Over a decade later, of delays, promises, threats, lawsuit, counter lawsuit, etc?

Her car was dropped off in her drive way, well, only some useless parts:  just the chassis, no engine, no trans, etc. 

She went to court again, and this time, the judge found her mechanic to be guilty to the tune of 151,000 dollars of reimbursement. 

https://www.thedrive.com/news/porsche-911-owner-wins-lawsuit-after-mechanic-held-her-car-hostage-for-11-years

https://www.dailymail.co.uk/news/article-13906385/academic-huge-payout-mechanic-porsche-returned-shell.html

Sure, a dealership is expensive. But, what is a quality repair job worth to you? 

If you're in Great Britain, avoid Jagjiwan Jhally  Engineering, just a lesson you can learn from someone else's cost.