I've noticed that my passenger side mirror indicator light is not working. Can i just change a bulb or do i need a whole mirror unit? Any help would be great thanks.

You need the underside bit of the mirror unit which is available separately. 20-40 quid depending on shape and whether or not you have puddle lights. Readily available on eBay or skodaparts.com and easily changed once cover and glass are removed.

Cover can be taken off with mirror in just make sure its pointing down, i bought after market and had to do some mods to fit next time will be dealer part.

This should give you an idea of what to do. Hope it helps.

Ok thanks! Just one question though, what's a puddle light and how can i identify mine has got it?

Its the white light lamp in each mirror underside that comes on with the locking or unlocking of the car. It tends to be fitted to higher spec models.