Thank you Willk! You were the catalyst for some late night Raymarine repairs on the kitchen table!
I decided what the heck, I aint paying somebody to tell me the switch is broken so I tore in at 23:15
I think being a 2005 or 2006 its well out of warranty
within 3 mins problem found, and also why the acknowledge soft key has been playing up for some time
£147 on ebay and I think I have hopefully fixed it. Should take a couple of weeks from the states but if this works I will have the smuggest face in the marina!