retro-fitting BMW heated grips from a C1 on a R1100S

[masha]

I have acquired a new set of OEM heated grips from a BMW (C1 of all bikes) and I have installed the heater electrics fairly neatly.

I am trying to remove the old grips and the hard plastic base they sit on. So far I have been unable to pop the control clusters apart and don't want to force them. Does anyone know the knack of dismantling these parts on the bars, then I can further check/test the suitability of the C1 grips

regards
Matthew