Well, I would start by making a list of what you definitely want in a car, what isn't essential but would be nice, and what things are important to you.
EG: must be able to carry long loads, must seat 5 in comfort for long journeys, must have ABS bags etc, must have cheaper road tax, servicing nice to have cd changer etc.....
Get a paper shortlist of all the vehicles that fit your criteria.
I don't know your budget, but if main dealers have similar cars on their forecourts, go and look at them, then go out and drive them all. Even if you are to buy privately, it pays to have a good sniff at a dealer.
Don't forget to take your list and make notes of everything you like about it (and those things you don't like too).
Don't be afraid to crawl all over them and (for eg) put the seats down to see how easy/tricky it is etc...
Ask about cost of servicing and anything else that is important. If your budget includes newer cars, consider a diesel if (amongst other things) you want to reduce your road tax bill. My 2002 1.9 Tdi is only £115 pa, and it's not in the cheapest band.
There will be compromises, but at least this way, you'll be able to make the best choice for you.
Personally, I wouldn't go for a Vectra, unless the latest model.
The previous generation had reliability issues, especially the early (N/P) models.
If you want a bread & butter car which will be easy to service, the Mondeo (new or old) is well written up. Don't know about the old one, but the new one is cavernous!
The Rover 75 Tourer is also liked and will be cheap to buy, but don't forget a discount.
I would discount Peugeot/Citroen as they are unreliable too. The difference being if a French car goes t*ts-up, they can be a nightmare (physically and financially) to fix - I know from experience!!
Zafira has a great write-up from the likes of What Car?. 7 seats and you don't have to remove any to gain more space - they all fold away.
Finally, don't be a badge snob - try a Skoda Octavia estate - they're great!!
No, I haven't got one really.....