The safety cell or Tridion cell is from the engine bulkhead
all the way to the back of the car, and in any other car
the damage would have been far worse than what you
have explained so far...in fact I'd go so far to say that you
are lucky you were in a ForFour as it sounds as if the car
would have folded right the way in at the 'B' post if it were
nigh on any other car !
Based on the damage details you have given it is therefore with
regret that I would more or less guarantee that your insurers will
write the car off, as to repair the stated damage will cost at least
the current value of the car in terms of parts, let alone labour etc.
So, it is with a sad heart that I have to suggest to you that you
start looking on Autotrader etc for a CDi of comparable year and
spec as your car for the current 'going' rate/price and accept no
less than that in settlement from your insurers. Stick to your guns
when they make you an offer of compensation as the first one will
usually be well below market value, and when you refuse they'll do
the usual of dragging their heels, hoping to wear you down over time
and that you'll just want it all to end/be resolved. Don't give in.
Obviously if there are any injuries etc to be taken into account, then
be sure you get the best in respect of those issues, as well as loss
of earnings, inconvenience, out of pocket expenses if you have to
use other means of transport etc etc etc.
Keep us posted on things, and we'll give you our support, ok.