rear window demister problem

hi, can anyone help, I have a k12 and the button for the rear window demister normally illuminates when pressing it, now the button doesn't illuminate. Does anyone know what and where the fuse is located ? I don't have access nor under wiring diagrams. Thank you
it may be the light behind the button, not the actual fuse ^_^
I think that fuse is most likely to be among those by the steering wheel
(as opposed to those under the bonnet)

Does the demister still work?
I really need to get one of those pen things off ebay/amazon to fix mine

(the circuit is broken in a couple of places across the window,
so the window doesn't clear veryt well in a couple of spots,
the pens have conductive/metallic ink to complete the circuit)
Hi my rear screen in not demistering ,the no cracks in the rear window isobars and I've checked the connections ? Lost...someone said the fuse for the rear windscreen to demist is located by removing the nsf headlight ?.. Anybody help

Thank you