It didn’t work for me either. I’m an engineer by trade and am competent on the tools. I’ve also been in the motor trade - working on and around cars - for longer than I care to remember.
I cut the mechanism open to gain access to the plastic gear, but had no success in it releasing the deadlock. I tried several times... The only option was to break the lock assembly apart so I could get to the latch, and then finally open the door.
Fortunately I had a spare lock mechanism that I’d previously bought for a Mk4 Golf - but never used. The general consensus of opinion was that the Golf item - whilst looking and being mechanically the same - wasn’t compatible, due to differences within the electrical side of things. However - and to my delight, in this instance it worked absolutely fine and all is now well.
Thank you to everyone on here and everywhere else for the help and advice. Most appreciated 👍🏽