Thanks Horace... The red piece of plastic... what a total muppet I am. There's me thinking I'm clever because of course i played with the button on both units and needed the red plastic to reset the button! Should have thought... As for the pun. Fnarr fnarrr!

I guess it makes no difference at all how the boot is actually attached given it's hidden. More violence needed me thinks. It's fortunately pretty easy to get access to everything as now I want to change it and I've made a ruddy mark on the leather of the existing knob which is going to bug me more. Thanks again