JAR Motorsports. They're on the Barbot Hall Industrial Estate, ROTHERHAM. Not an official merc indy, but they've done amazing work on my car, just had b service done, with 4 tyres, new brake lines, fuel lines, think it was just over 600 quid. Recently I had all the injectors done , fuel rail replaced, fuel pumps rebuilt, and a tank drop and flush and reseal. Worked on it for 2 days and nights, bill was just over 250. I have had a lot of work done so maybe they were doing me a deal, but still...
Can't recommend them highly enough. Ask for John.