On all estates, even leather, the rear seats fold flat and lock in the flat position.
On pre mini-facelift you have to remove the rear headrests, press in the little latches at the back of the socket tubes and pull headrest out. Will be stiff if not done for some time, bit of polish on metal rods helps keep them free.
Mini face-lift press the button underneath the headrest and it will fold forwards.
Face-lift Think its the same as mini-facelift.
All models, press in the button to release the seat back (also release latch holding split seat together on face-lifts) and fold the seat down, at this stage it wont sit flat, now press down or kneel on the seat back until the flap bridging the gap between boot floor and seat back locks into place. Hey presto a full size double bed space!!
To fold seat back up you have to press down on seat back again whilst lifting the flap.
The proof that seats fold really flat:

You need to get a rear Door fitted to that Mate, otherwise all your stuffs gonna fall out!
