I'm going down your list in order here...
The boot isn't huge so if you've got 4 adults plus a dog in the boot you'll have very little boot space for anything else. But it's very roomy in the cabin, including for rear passengers if you fold the middle seat into the boot and slide the seats back and inwards.
32k on a 4 year old car is very low mileage. To give you a price comparison I bought an 04 plate, 1 owner, mint condition, 2.0TDCi Zetec with 32k miles and FFSH (but due its annual service) last march for just over £6000 from auction, so I'd expect you could pick up a 1.8 petrol for £4000 if you really wanted to. Have a look at this website www.smag.co.uk/
it gives you prices of cars which have recently gone thru a public scottish auction (click the past prices on the right). This is the place where the dealers buy the ex-mobility or ex-lease cars for their forecourts. Remember there's an extra couple of hundred quid on top of the auction price (and that you have a limited guarantee).
Owners reviews - Have a look at www.ffoc.co.uk
forums. Also compare other manufacturers of similar type/size of car (like the megane scenic at www.renaultforums.co.uk
etc) and compare how many problems you find for each car in your bracket. The Ford's dont have too many problems in my opinion. Sure you will get "unlucky" cars but thats the same across the board. If you really want reliability then go for something japanese - like the similar sized mazda (whatever it's called).
To sum my C-Max up...
Pro's - It's great to get into and out of. The seat height, position, comfort and leg and shoulder room is great. It's smaller than it looks so is easy to park. It's quite cheap to buy. It handles great.
Con's - Fuel economy isn't as good as the official figures. The dash rattles a bit. The padding could be better. The boot isn't huge.
I've now had mine about a year (10k miles) and haven't had to spend a single penny on it (except the service mentioned earlier which I did myself for about £60 including the expensive oil and the filters). It's due its MOT and I'm not even checking it over first as I'm so certain it needs nothing.
Go buy one - but don't necessarily buy from a dealer. Sure you get a warranty but if you save £1000-£2500 buying privately or at auction then you have that extra couple of grand to fix anything that MIGHT break. Buying from auction ensures there is no outstandingHP etc.
I'll just add here that I'm not a "Ford Man" (in our family theres currently Ford, Renault, Vauxhall, Mercedes, Volvo) but I'd certainly consider a second C-Max.