How to fix siezed air blower switch 2008 Peugeot Boxer?

I have motorhome based on a 2008 Peugeot Boxer 2.2 and the air blower switch has jammed or seized. It can be forced left or right slightly and the fan will run until I let go of the switch. The switch is part of a unit containing heater and A/c controls. Is it possible to replace the faulty switch or do I need to get the whole unit replaced which I believe will need a complete strip of the front dash.

Any ideas for resolving this ?

Johne
July 2014