Hi all,
A positive update for everyone. Happy to report I managed to fix this yesterday!
I popped the switch out of the car and then removed it from the housing. Inside was a silicone cover with some contacts and a circuit board. There were a few black dots on the contacts, corrosion I assume? I used some isopropyl alcohol and cleaned both the silicone cover and the circuit board, then sprayed the board with the Servisol Super 10 (Kontakt) switch lubricant. Let it dry out then put the switch back together and back into the car. Worked instantly!
Like I said before, I don't know cars or electrics but hopefully I've used the correct terms with how I've described it. I've attached two photos of the bits before I cleaned them if anyone is interested or it helps anyone in the future.
Thank you to everyone that commented, really appreciate the input.