I have just obtained a solution for this problem from Malvern.
All series III car owners (the cars without the "coathanger door opener") need to do is take the exact internal width dimension, obtain a rope or wire for that length PLUS say 200mm either side and tie internally from one door to the other and voila, you're secure.
To open doors just undo knot. Pls remember do NOT use double knots (makes it awkward) and you only need to undo from one side only to release and enable you to get out.
Nice to have a simple solution to this issue. Yr thanks accepted in advance.
With a big <img src="/forums/images/graemlins/wink.gif" alt="" />