S reg golf can't open passenger's door?

For a while, every now and again, central locking would forget to open passengers door but you could poen it from the inside... sadly now it never pops the thing up and you can't open it from the inside or with key on outside... the little knob thing is under huge pressure to stay down when you try to pull it up...
Can anyone help??
Just had car serviced and mot so money is very tight to put into the garage again.