Swung by the local 'Volvo Specialist' in my lunch break to ask if they had any thoughts. They kindly phoned the local Volvo dealer to see if there were any software updates available, which there aren't for my car for engine/gearbox.
They said they would not change the oil in the gearbox as if you are changing it to try and fix a problem they have been advised by Volvo that it will only make things worse.. They also advised that if there is no fault code indicated on the dash then they wouldn't do diagnostics as basically chasing your tail and costs could spiral with no result.
Phoned Hutton Bros near York (who I've seen highly recommended elsewhere on this forum) and they will do a sump dump for £190. Think I'm just going to do it myself.
Can anyone confirm this is the correct oil?
https://www.ebay.co.uk/itm/202346084136
Thanks