You can get a thing from Belkin that goes into your cassette player, fits both front and side-loading players, and plugs into the speaker hole in the iPod. Then you get a battery charger that goes from the bottom of the iPod to the cigarette lighter so you are running off the car battery instead of the iPod when playing. I got them both in the states at Target, great investment and you should be able to find them easily here. That's what made me want to get the stereo hookup cause it is really cool to be able to listen to your whole cd collection at the once.
You can also get a doohickey that plays the iPod thru your car's FM stereo but I have heard dodgy reports on that, it's much easier to just go direct via the cassette player.