I used to use "Independant Mercedes Specialist" aka Chris Gray.
He used to work from his home premises then moved to a unit but last I heard was about to move back home.
He is knowledgeable and good at his work. Chris permformed faultless maintenance to Mercedes schedules (down to the greasing of latches) using MB parts, retro fitted my cruise control and replaced my gearbox.
HOWEVER. My last few experieinces saw him get busier and busier and frankly unable to cope or manage.
My last experience was having my wheels damaged whilst in his care. I believe he had the best intention to resolve this suitably, but lack of effort probably due to mamanegment of his time meant this never occured. I sourced wheels on his behalf at a good price but never got remimbursed properly. It was only as I had a bill to settle that I managed to end up roughly quits, although never got some of my missing paperwork that was "in the post".
I wrote to Chris and while staying friendly, told him a few truths about what I expected. This was met with instant promises that never materialised.
It was a shame to see and it could be the case this was a temporary phase combined with poor luck for me and the business may be better run now.
The last service I had for my car was from JP Marques in Aston Clinton. Good level of service, had required equipment, reliable and trustworthy, collected and delivered vehilce from my work. Welcome reassurance of a properly presented premises.
I later sold my car to them. If I had not sold the car, I would be returning to them for servicing and maintenance.