I would fit with a switch under the seat if a live hotshoe anyway just in case as any extra possibility of any battery drain and you join the flat battery club.
If you are on the switched live and not direct on battery obviously this is fine as the key is your isolation point.
Thanks for the advice. I had a look at the fuse wiring and it is very tight and cluttered under the seat. I then had a think, 'what else comes on when you switch on the ignition? The lights' So I wired it on to the pilot bulb wiring. It works a treat and is very neat.