Do not use intermediate switch as it is not, on off ,its a change over switch eg possition 1 , L1 to L1 ,L2 to L2 possition 2 L1 to L2 ,L1 to L2 so if ou use this and switch it you will either cause a short or more likely change pollarity of power to lights.If you want some clever switching get to b and q for 20 quid you can get a remote control water proof external socket .one last thing is the circuit rcd protected.