Colin I was admiring that very car last week – what a brilliant colour, wish they sold more of those :(
The general rule to anyone who asks me about possibly buying a Vel Satis is… avoid the 2.2 dCi and you'll be good
It is an incredibly badly designed engine, and WILL suffer turbo failure at some point, no matter how well serviced and cared for. EGR valves, injectors and all sorts of other oily issues plague them as well. Even if you do see evidence of it all having been carried out, I've seen cars that have had 3 turbos. Have a read of this – should tell you all.
The 3.0 dV6 and 2.0T petrol are both good engines. The former can suffer head gasket failure and overheating issues, while the 2.0T has a turbo to go wrong, but little else.
For ultimate reliability the 3.5 V6 is the way to go. There's also the bonus of it being chain driven so no costly belt change to factor in. Fuel consumption isn't great, but performance is
Other areas: Noisy rear suspension is the norm. People have spent hundreds trying to cure it and failed, it's something that we just have to live with, it seems. Another common failure which has just surfaced is the radio – I have three Vel Satis' and none of them have a working radio. Yet to find the cause.
That should be enough to keep you ticking over for now