Thanks folks, I was most the way through the disassembly process and had to stop as the base cover would not fully release. There was a spot at the back left corner (if your were looking at the laptop keyboard from normal typing position (right back corner if you were working to remove the back cover from the bottom)). It seemed to be stuck, is there an insulating pad that might also be an adhesive when heated? I was forced to give up as I found no clips, latches or screws holding it in place.
What was preventing the back corner of the cover from releasing please?