I used to have a renault megane and will be returning to it when it is finally fixed up again. I was able to keep a very large 3 wheeler in the boot and still manage to squeeze a small umbrella fold maclaren in there if it was angled right.
No probem with pushchair but dont rate the car that much.
It has loads of manufacturing faults and a common one is that the boot lock can go and you are unable to open it from inside or out. This happened on mine (along with loads of other problems) and I was unable to use the boot anyway unless I threw stuff over the back seat. It was mega expensive to get fixed
There was a forum I found at the time and it is a common problem.