If we are going for a Citroen anyway (seems the best way to make the money go further), which one would you go for?
They have roughly the same mileage (30-35k) and a similar spec. All 3 would fit the kids in and fit our requirements, tho I still wish we could just jump straight up to a 7 seater! Realistically, if we DO decide to go for 4 kids (looking doubtful right now), it will be 2-3 years before #4 arrives. So maybe it'll be cheaper to run a 5 seater till facing that issue!
We've done test drives in the Berlingo and Grand Picasso and enjoyed them both - the Grand was slightly more comfortable but not hugely.
The main difference for the money is in age. For roughly the same price (around £7k) we could get:
A 2009 Xsara Picasso A 2008 Berlingo A 2007 C4 Picasso
OR a 2007 or 2008 C4 Grand Picasso with a lot more miles on the clock. OR a 2005 Touran with less than 40k on the clock. But stop your dreaming woman.