So the door unlocks fine with the key and occasionally with the Central locking button! I don't get the light buzzer anymore either!

Am I right in thinking that it could be a switch and not the whole licking unit??

Light buzzer is probably microswitch in the lock mech, not available as a part in itself but you can get something suitable (maplins) and get it in. Or just get a pattern part mech (much less hassle). Your unlocking issue I suppose you could be really lucky and either need a new battery for your fob (not unheard of) or just have sticky mechs. Door card off and lube the hell out of them. Or you could be unlucky and it's corroded pins in the multiplug. While you've got the card off unplug it and have a look.

Right oh, like I say it's only the driver door and works fine with the key in the lock seems a bit daft

The wonderfully strange world of Octavia mk1 central locking eh...

Might just try a new mechanism from ebay for £18

Probably a good place to start!

If the micro switch has gone could it be not locking the door as it thinks it's open??

Most people go for those mechs and I've not heard of any problems. Grease it up good before fitting to keep sticky catches at bay for longer.

To be honest I'm not sure, it's definitely worth a shot. You can check the multiplug while you're at it anyway. Sounds like if it is a corroding pin it's not completely dead yet so you may be able to clean up the contacts. I know when my microswitch went it only effected interior light, lights on buzzer and door puddle light when door opens. But not all the time or all at the same time weirdly. My passenger door locking was just sticky catches. Lubed up and still fine 7 months later.

Well I bought the ebay mech for the passenger door and since the day it arrived it's been spot on (6months ago)despite never going near the car so hopefully when the other one arrives in the post it'll fix itself lol

Voodoo lock mechs, like it. Maybe you should get the spare mech out and give it a rub, make a wish or sumink.