Well, I am sat out in the sun with a glass of red, contemplating the next 'work' to do/have done on 'Zeb'.
The 'knock' is greatly reduced down to, say 4-10 seconds after start up . That said, since last posting the knock had returned with a vengeance and as I had it (rightly or wrongly) I poured in the so called 'seal comditioner' . Which appears to have greatly reduced the noise.......
It is still niggling at me though, so I have ordered the sump seals from FRF Volvo and some sealant for the sump from GSF. Got spare Volvo filters already.
Have seen the 'how to' on matthewsvolvosite, which does look a little daunting from my view point.
Also have developed a juddering on braking at high speed, can be felt right through the car. Brakes are as new all round, so thinking maybe a bush or two is at fault here.... Not sure.
Anyhow, Chris 'my mobile mec' is dropping by during the week to do some diagnosing.... Will have a chat with him about the seals & may just come to an agreement on price where he does the work with me as general dogsbody and teaboy! 
 
 
Have also just started to bring the body back to nice and shiny, using a cut agent, then polish followed by Collinite 476 wax. Only done bonnet and wings so far but am chuffed with how well Zeb is 'coming up'.
Hoping to get all the work done soon as Zeb has to tow the caravan to Kent again later in the month......