I tried again and DID manage to slip a credit card all the way into the
door frame so I could slide it up and down. It won't let me slide where
the latch is though. I've used pliers to turn the handle as far as it
will go but, checking with the credit card, that latch is still very much
sticking out so it looks like that's definitely the problem... I can't
shove the card in where it needs to go though to force hte latch back in
no matter how hard I try...

Hi all

Problem solved! My mate who's a wizz at DIY and stuff came round and
continued my work with the credit card and succeeded in getting the door
open! He said I'd have got there eventually if I'd have kept on trying...
He took the whole lock mechanism out which he said had broken. Did some
jiggery-pokery and now it's all fine again. PHEW!

Thanks for everyone's advice