Central locking and immobiliser problem

[seacoff]

I have a 96 A4 1.9tdi. I've had it the past couple of years and lived
ok with it's little bugs. Other than spending lots of cash fixing it I
was wondering would anyone here be able to assist me.
Problem no 1. The main key was lost before I got it so I have been
working off the spare. There is no alarm installed. When I go to start
the car it's like tossing a coin whether it will start or not.
Sometimes it'll start 1st time and other time it takes about 20
attempts but it will always start. It turns over alright when I turn
the key but it doesn't catch. I was told by a mechanic that when the
key is turned a signal is sent to a chip in the key by the ignition and
if the key doesn't respond correctly the immobiliser stays on. Could
this be true? If so what is a man to do?
Problem no 2. The central locking. When I open the drivers side door
supposedly all the doors, boot and fuel cap should unlock , this is not
the case it's started to fail on me . It's as if the central locking
has gremlins and will work when it wants to. Maybe its something to do
with the chip in the key. I dunno. So in my moment of desparation I
write this as the fuel cap is locked and I have absolutely no way of
opening it? OR DO I?????????

Thanks for any insight.
Sean