Similar - but different!
I have a 147 3-door (pre facelift model) with a similar problem. The remote key has never worked and is ridiculously expensive to replace. Manual locking and unlocking is fine but recently the electric tailgate release became intermittent in operation, requiring more and more button pushes to operate, and has now ceased to work. I have replaced the entire locking activator mechanism with a guaranteed working unit but nothing has changed. I have replaced the bar containing the activator switch (below the card drawer/drink holder area) with one that is known to be working, again without success.
When the tailgate switch is pressed, there is a very faint click that can be heard and seems to be coming from the right-hand side of the dashboard in the general area of the fuse box. I don't believe it is a fuse problem as the deterioration in the tailgate release was over a period of time and a fuse would have been instantaneous. Is it possible that there is a relay somewhere that has failed? I've tried to find a wiring diagram for this car but without success to date. Any suggestions as to where to search next would be gratefully received.