I must be! :-))) It did occur to me on the way home...
I saw the leak with the car on the ramp.
It was very convenient as I had other, smaller jobs to do there. I had a "safety check" done (Free!) and this was identified.
Saves me some to-ing and fro-ing. I do have a fairly local indy workshop but I have mixed feelings about him. Whenever I do the annual roadworthiness test ('MoT test') there I get charged the statutory fee plus some labour without anything else being done, apparently. Merc charges only the statutory fee or does it for nowt' with a service, though about 40 pounds off a service or other larger repair job is not that much in comparison with a cheaper indy job.
Maybe time to look for another garage.
DAS
For direct contact replace nospam with schmetterling