check the button has not come off the printed circuit board easily confirmed by shaking the fob first(rattles) or the solder around the switch has not cracked due to fatigue.
Rover before its demise wanted £160 PLUS A REPROGRAMMING FEE for a new key,as they said old one could not be repaired In my old fob the switch was totally detached but still got re soldered back in position in less than 20 seconds with a fine point soldering iron.Did I feel smug, easiest £160 smackers I had saved for 20 seconds work.
wirecutterman
July 2009