Look at this video. In Sink Erator Food Waste Disposer M55, 0050375002123
It looks like it is a pretty atandard switch wired a bit away from the unit pretty much where ever you want it.
Think the long and the short of it is use a waterproof switch if your going to put it somewhere likely to get wet all the time.
If it's being put somewhere a bit more protective then just use a standard switch.
Hope this helps
Wizbit
BS7671 does not exclude sockets spurs etc from being installed under sinks etc. The equipment must however be suitable for the environment.
In my opinion, best practice would be a splashproof switched spur feeding the waste disposal but only because theres a possiablity of switching on/off with wet hands.
A normal switched spur located away from any potential leak areas. Oh yeah make sure the sink unit is sealed properly.