Diesel Specialist in Hertfordshire?

[spinningfish]

Sorry to post both here and in the Ducato section, but I'm desperately trying to find a decent, competent Common Rail Diesel Specialist in or around the Hertfordshire area that people have had a good experience with.

I've been to two so-called specialists now and have spent a small fortune, with the exact same fault remaining.

I'm self-employed, with this one vehicle for the business and it's putting me into the red.

Thank you!