This all despends on the situation, personall I'd turn up at a car dealers in the C Max (clean the car first) and then see what they have available. I'd be sure to take along the baby and stuff that I had in the boot ot at least measure how much boot space you would need first.
Alternatively, the virtual option....
I'm sure I've used this link myself before, many moons ago, here is a good one for seeing what you may like, with reviews as well.
http://www.parkers.co.uk/choose/Wizard.aspx