Really simple fix. I found a small art brush buried in the bottom of my tool box which was similar diameter to that of an ink insert for a Bic Biro pen. You then lift the handle up two thirds of the way and look behind the top of the cover, you'll see two metal looking clips which are attached to each other in the shape of one long metal slider. The slider/clips move from left to right to open and the other way to close; I inserted the handle end of the thin art brush and pushed the slider to the open position. This made the handle really loose and you can pull the top out a couple of millimetres which allows you to then move the door handle cover downwards to disengage the bottom from two hooks.
Once the cover was off I just pinched the ends of the slider inwards a little to gain more purchase onto the handle cover and then re-assembled, you slide the clip right to left from the other side of the handle to secure the cover. Problem solved and all done in 5 minutes, I don't even think that I can justify a cool beer to reward myself it was that easy
If there are a few others out there with this problem then I could dig the camera out and do a proper 'How to DIY' write up for it for it.
