Smaller MPVs are going to be series 1 or 2 Scenics or the Picasso. With the seats down they are as big as a small van inside and the loading space and shape is much easier than any estate and they are a lot taller inside. The Picasso is a truly miserable place to be though, according to the two people I know who have had them. We had a Scenic 1 and it was comfortable and very economical. Go for the 2 litre and avoid the Scenic 2 which was apparently built out of Brie. Don't get an auto.
Next size up is the Zafira. Her folks had a diesel one. Truly sounded like a diesel and got shocking mpg returnZ but it was a proper workhorse. They abused it for years and it just took it. One day all the warning lights started coming on and they decided to replace it as the main vehicle but keep it until it died. It didn't and they've still got it, unwashed, unserviced for about 3 years now and it's still soldiering on.
Next size up is going to be the Espace. This is quite a bit bigger than the Scenic and any mid-late-90's survivor from when Renault actually screwed their cars together properly will, basically, never let you down. It'll seat about 50 people, all the seats come out and it's as big as a Merc Vito in the back.
You'll get any of them for under £1000