I've read some not-so-great reviews about Simonstone in the past, so having just got my car back from them, I thought I should post to even up the score a bit because I've been really pleased with the service I've received this week.
The car went in for an elusive knocking noise at the rear and to cut a long story short, they found it and corrected it all under warranty with no fuss - much quieter drive now. Apart from that though:
On taking the car in, without prompting, sent an engineer out with me to hear and confirm the noise. I explained that there were a few obvious things I'd checked already and wasn't treated with the hostility that is sometimes the case when you venture an opinion about where you think the problem might be.
I was provided with a decent loan car at no expense. Although they kept my car for a few days to get to the bottom of the problem, I was called at the end of every day to update me on their progress.
They ended up completing the job one day earlier than estimated and called me to let me know the car was ready to collect. The car has come back clean and tidy.
Little things, but makes all the difference. So thumbs up from me