Its alot more than just a switch lol
Behind the dash is a magic box which connects to the switch and the wiring loom and adds the light sensor so it can work
You can get them on ebay - they are designed for a mk4 golf, but work perfect on the polo
It also gives you coming home and leaving home lights
Functionality wise, its as good as what comes on the newer VWs with auto lights!!
Heres the link
http://www.ebay.co.uk/itm/VW-AUTO-HEADL ... 3380ec5889
The kit will work on most VWs with the same style headlight switch connector.
The switch is from a Mk5 Golf - comes with the kit.