I know the 'how much is my car worth section' is closed. From a completely different angle - no figures - my recent experience is that demand for petrol Vectras is falling while demand for diesel Vectras is astonishingly high. I should know, I've spent since April trying to get a diesel Vectra and I've lost out by minutes several times even though I've been quick off the starting blocks. Problem is the diesels with decent mileage are sold as soon as they are advsertised, while even ultra low mileage petrol Vectras are sitting on the forecourt unsold. I can point you in the direction of a 2008 Vectra which has less than 10k on the clock and it has been sat there for about 7 weeks, nearly 8 weeks. In contrast, a 150 diesel came in on Tuesday, went on the dealer's webiste Wednesday, was sold by Thursday!!
The underlying reason is of course soaring fuel prices. There is also the added benefit that the life expectancy of a high mileage diesel will last longer than a petrol as people tighten their belts and change their cars less frequently given the capital cost involved.
My petrol Vectra is immaculate (not biased) but even in immaculate condition dealers aren't interested given its mileage. However, if it was a diesel with the same condition bodywork they would be very interested in buying my petrol Vectra. A dealer told me he scours the market looking for diesels every day as he knows they sell as soon as he can get them, but not petrols. Petrols are, as you would expect, depreciating but diesels are appreciating i.e. they aren't just holding their value month on month, they are increasing in value month on month, and again that is my experience since April, diesels have increased in price.
I couldn't get a 2008 one, kept losing out to someone just a fraction quicker. I've now put a deposit down on a 150 diesel, a 2007/07 plate. I will pass the petrol one to my wife and I'm looking to munching motorway miles in the 150 diesel and that will make us a two Vectra family!!