I have 3 kids and two still in car seats and manage fine in the clio. I just fit the younger one in the front and make dad go behind her.

but that is mostly to stop my little dears fighting as she does fit okay in the back. she is 3 now so her legs are loads longer.
Also fit loads in the boot, pushchair and I have my tool box and cleaning box in their half the time too..and I get my shopping in.
When I had a tiny baby I had a metro and I managed okay in that too although swapped due to the crash ratings.
think it depends on the pushchairs but remember they go out of the newborn stage bit of the pushchair VERY quick. get one of the car seats that has the lock system and then its easy peasy to get them in and out. I actually looked for a lightweight pushchair for my last child. It did everything I needed too but fitted no probs in the cars I had. Sure a clio boot must be at least as big as a cinq sporting or metro boot, both of which I fitted my pushchair in.
I do also have the zafira though. And 3 doors maybe a bit of a pain when very small but trust me as a mum I find 3 doors LOADS better as they get older. No windows or doors to mess with.