Thank you all for the advice.
bigmac95kt - It's great to hear that there are people like Pianoman who could be consulted if necessary.
andyfr1968 - I think you are right about the washer, as I recall the gunsmith telling me that he had a make one.
thursodog - warning noted. When I picked up the gun and asked him about the power, he told me it was near the legal limit - no chrony figures provided
and as I dont possess one cannot be sure. It certainly doesn't have the 'yellow pages' penetration power of my HW95S ;-)
I will also see who else might, gunsmith wise, cast an eye over i