Simon - Certainly talk to the service guys at Volvo - (I would not bother with the sales guys - no disrespect to them but they could be more interested in keeping the sale simple rather than complicating it) and I would get them to change the transmission fluid and any filter in the auto box.
When you are buying an auto check the auto box oil - if it is opaque, dark brown, smells "burnt" - walk away. It is on borrowed time.
If it is clear, smooth between your fingers, and just has that pleasant oily smell - you should be ok.
Check the service intervals and make sure that the auto box services were carried out. The oil in the auto box is special stuff - and whilst it is not expensive for some reason a lot of people do not bother to change it but the whole gearbox depends on its ability to change its viscosity with heat.
Think of a saucepan with milk and custard powder in it, when cold you can stir the liquid no problem, when the heat gets to the custard powder and heats it up it thickens and if you continue to stir the liquid, in the end it will get so thick that the pot will start to turn on the hob. You now have drive!
Auto transmission fluid does the same but when it cools it reverts back to normal. However when it gets old and dirty it stops working properly and the box will wear out remarkably quickly