Rear side passenger door wont open

Hi All

Thought I would get a second opinion, a while back I noticed that the rear side passenger door was not opening and when I asked our family mechanic he said that it is a common fault on the Polo's. He said it happens when the deadlock does not disengage and then remains "locked".

To fix it he said you basically need to rip the door of and replace all of the insides costing upwards of £300+

Surely there must be a better way than to have to destroy the current door? I want to fix the couple of issues with it before I sell it but don't obviously want it to cost me a fortune to do so.

Thanks