Tailgate Lock Problems

Hi, I'm having trouble with the tailgate lock on my Defender 90 (2000 model).

The lock doesn't lock with the key any more or the latch inside. I've taken the assembly off and tried to remove the lock barrel to replace it.

According to my Haynes manual this looks v. straightforward but I can't get the lock barrel out.

Any tips?

Also I'm struggling to find someone in UK who can supply a whole new tailgate lock assembly - any ideas?

Thanks!!!!!!