My very first service was with Mark and I must say he had similar dedication to his works as well. The problem he seemed to have was his workshop under-staffed. At most of the times there were only maximum of 2 ppl working including Mark so he never had enough time dealing with all customers and was contantly getting interupted.
However every time I took my car there since it was stock I was quite happy with the works done by Mark eventhough he usually took longer than what was originally planned. These were about 2 years ago so things might have changed now. I had fuel pump and FMIC installed by him and he did good job for both of them. Haven't tried getting tuned by him so can't really comment.
I've heard a few "different" perspectives about his workshop but I would suggest if you want to make sure jobs for your car are done properly they have to be done by Mark himself, not his apprentices or assistants etc
Keep us posted with your tune results Adam. It's looking good so far