You're putting the cart before the horse. No point looking for replacement starter switches before you've diagnosed the problem. It might not be the switch, but if it is, the contacts probably just need a clean. Come to think of it, something like that is a likely scenario given that you live close to the sea. It's not unusual for brass contacts or connectors to get a bit corrosion on them in marine environments.
As with any electrical problem, follow it logically. There's two circuits to check:
One, the high current (big fat wire) from battery positive to starter relay, starter motor and back to battery negative.
Two, the low current control circuit from battery (via fuse) to starter switch and starter relay and back to a ground connection somewhere.
One of the simplest checks is to bypass each circuit and see if it eliminates the problem. The only tool you need is a piece of wire. In the case of the starter motor circuit, a piece of BIG wire, like a jumper lead.
If you're not confident to delve into the bike's electric systems, have a go anyway. You might learn some new skills. What could possibly go wrong?
If you decide you need someone else to come and look at it, I'd be happy to do it (I'd like to visit the Channel Islands). I'd only ask that you cover my travel costs from Tasmania to Jersey and back.
