Hi Henry,
not sure if I am writing in the space for you to receive my input. Seems like you already know of McGraths, who I would thoroughly recommend, however there diagnostic kits have limited scope, for a problem with my Granturismo that they couldn’t fix, David kindly organised contact with Jardine motors of Colchester. Over the course of the last few months they have gone away from Maserati and solely Ferrari but, they have retained the licenses for the specialised diagnostic equipment and were able to sort out my problem. Cost, just over £200 inc’ vat for an hour for what ever they did, May sound like enough but I guess it’s about the going rate and their efforts have worked, so far. Dave Jenkinson