Hello. I'm in Norwich and have pondered using Strattons over the years but never have. I've always decided to go somewhere else (I take my GS to Autoshield!). However, if I needed to use someone local then I would go to them.
They recently inspected my GS when looking to trade in against some of their stock and even the sales chap seemed to know what to look for. Apparently they have a few maserati owners who use them. Good friendly service and not heard anything negative about them except being a bit pricy (not sure I agree).
Alternatives would be STR who I know look after one or two but didn't really impress on a couple of jobs they've done for me. I would probably go to Alfashop over them who look after our Alfas and I would trust them to the odd straightfoward job.
They are a good place generally and do look after their customers well. They're better known for Aston, Lotus and Morgan. I think I'm correct in saying that the "old man" has mostly passed the business on to "junior" now so that he can still dabble with their race team. I know they were looking for one or two new staff for the workshop recently, specifically for their restoration work. Between them and STR, I think I'd probably go with Stratton by reputation and the fact they're used to dealing with higher end cars more regularly.