The RCCB relay will most likely be tripped, (Residual Current to ground - protection relay, if you have such a thing in GB?) This could happen even if no one actually touches the outer surface of the switch. Even a very high (Kilo-ohm range) connection to an artificial ground can trip the relay, so the CF fibres are easily conductive enough to "tickle" you, and trip the relay .. depending on the connection and CF fibre resistance, you may get anything from a sharp "sting" to just a tingle, both with the annoyance of loosing all power in the house and having to find and reset the RCCB.
Of course, none of this will happen if the back of the switch plate has some (even a thin) layer of insulating resin --
Better safe than sorry? I would certainly not welcome a lawsuit form someone who bought the very nice lightswitches, and got "tickled" by 240 V -- or had their freezer cut out when on holiday - 
I was a partner in a small company some years ago, who made and installed "power controls via the internet" systems .. Our system developed a fault that triggered the RCCB and blacked out a Vets clinic ... They had two very large chest freezers, containing all the euthanized animals prior to sending them to destruction .. Lets just say that the clean up cost the company a fair bit of money ... 
"Sapere Aude"... Dare to KNOW!
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Do not adjust our mind, theres a fault in reality :-)