Apologies if my posts are incredibly rudimentary for most folks on this board, I'm learning as I go so appreciate you bearing with me as I muddle through.
The switch is back in and wired up and battery reconnected. Now, instead of the motor turning over I'm getting a noise similar to clicking sound when trying to start on a weak battery. This is a RHD 110, the noise is coming from what sounds like the footwell/firewall of the passenger side. I still have the old glass fuses and all appear in order.

Open to thoughts on troubleshooting and likely culprits?

Gotta laugh, this started as a quick 'n easy binnacle upgrade and now.... I have a 110 that won't start!

Battery flat? The clicking is probably the solenoid on the starter motor, it's a small female spade connector that energises it, check that's on nice and tight.