I don't see what's wrong with an email especially if you know you'll be disagreeing, it's better to have a record of what both parties say. I sent an email in the first place because I wanted to show the photos. I've no issue with speaking to the manager, I've already been back twice, once because I thought the new clutch was noisy and another time to have the clutch bled and an OEM hose fitted instead of SS one. Then I did call or went it in to see him. This time is a bit different because I knew I'd be basically saying his guy didn't tightened the bolt, he'd be saying he did. From that point, you can just go back and forth, or if you're communicating via email, it's easier to point at links and include info as to whether or not the plug can come loose after being tightened correctly.
As for the manager seeing this thread, I'll be linking to it anyway.
What do I want to happen? I want the £20 for cleaning up the mess that they should admit their tech is responsible for. Also supply the new gaitor (I'll get it fitted elsewhere after all this), they were under my car twice for a long time working on that area. Jez spotted it in 2 minutes. How are they sure it was already in this condition? (as he stated in the email response) and if so then surely they would have told me... just seems a little weird.
I'm just going to link to this post to prove the what common sense would tell anyone, the plug can't unscrew itself and then it's up to them to decide what to do.
Basically what Dan is saying is that (with respect) everyone HATES a keyboard warrior.
A phone call establishes a personal connection between you both, one that subsequently ( unless dealing with a *****) allows empathy and reason to enter the conversation.
Also if you can keyboard warrior him.......then he can keyboard warrior you because that ends his part of the conversation. If your on the phone someone has to end the call.....if you're not happy with the resolution then it won't be you will it? It takes some kahunas to hang up the phone on a disgruntled customer.
Finally you've not even told him what you want from him. Admittance of guilt will pure and simple not happen but if you tell him you're looking for 20 quid for inconvenience and a new gaitor I'd bet my bollocks to a barndance he'll give you it.
A mistake was made.....you have the facts to offer up him which 99% proves his tech did not tighten the bolt. The 1% is that you or someone else may have fettled with it in the mean time.