Have you got a five-door Fiesta? If not, don't get it. Just...don't. I fitted ours into MIL's Peugeot 3-door and nearly fainted from the effort (it was about 80 degrees though!).
Also, do you have a lap belt in the centre of the car? They need three-point harnesses to work, so you'd end up with the seat across the whole of the backseat otherwise. Mind you, they're great seats - DS was always very comfy in his in the car. Otherwise Bebeconfort do one that fits the Loola pushchair that is rear-facing but very 'lie-flat' iyswim. I'll see if I can find it (but will have to look later - DS needs his last feed!)
The Bebeconfort seat I was thinking of is the Creatis. It fits on the Loola pushchair.
Have you been to Johnston Prams ? There's lots on there about how to fit them flat in the back seat - basically you need two three-point harnesses, one each end of the seat when it's lying flat, so if the middle seat's a lap belt, it will have to be the offside and nearside rear seatbelts you use. In our car (a Honda Civic), it lay across two of the seats as the centre belt was a three-point harness. That meant there was enough room for me to sit in the spare seat (and get DS out and feed him in the 7.5 hour traffic jam we sat in from London to Kent while some fool decided (eventually...) not to jump off the QE2 Bridge...!).
He was only five months old...which is good in one way (slept for two of those hours)...and awful in others (couldn't explain what was going on...needed to drink water cos of bfeeding and needed to wee cos of enormous bladder caused by water needed cos of bfeeding!!)!