I would recommend the same thing I would to anyone in the U.S.-- do some research! Check out sites like AutoTrader.co.uk (which will also give you a good idea of price ranges for new/used models) and the various auto review sites. You'll fairly quickly see how the various makes/models correspond with vehicles you're familiar with at home, and the review sites can offer good comparisons of several models in a class.
Following up tmfigy's comment, I've driven a Zafira as a hire car. Vauxhall is really just a fancy, British name for General Motors, so you'll notice that a lot of the cars look very familiar. Unfortunately, so is the build quality. That means lots of them are just fine, but there tend to be lemons. The one we had was a bit of a lemon, which put me off, but I will say I liked the vehicle overall, and thought it handled pretty well. It is just a touch big for a lot of the small parking lots you find here, though, and while the fuel economy on the diesel we had seemed alright for the week we had it, I don't know how that would stack up over the long-term, especially if you're in a lot of stop-start traffic, as opposed to on the motorway, as we were.
Similar, though slightly smaller, vehicles I've looked at are the Vauxhall Meriva (seems eerily similar to my old Pontiac Vibe, which I really liked) and the Nissan Qashqai, and I'm sure there are lots of others. I'll admit I tend to be biased toward brands that I'm familiar with (Ford, Honda, Toyota, etc.), but I've had a Renault now for a couple of years, and I do quite like it.
Good luck!