I've used Croydon Minis a few times over the last few Months. They've always been really helpful and even when busy they've found the time to help.
They are not the cheapest garage you could go to I'm sure, but I guess you get what you pay for. they've helped me out of a few issues, including sorting a fault out the day before the L2B!
Moving to Devon next week! So won't be using them in the near future, just wanted to recommend them. They know their minis...
Philip