My 2000 GS300's cassette player keeps ejecting tapes without playing them. Any ideas, anyone? I've only just bought the car.

Have you tried reversing the direction of play before it has a chance to spit it out? Or tried a tape cleaner through it?

Could it be that the emergency eject is stuck? On nearly all cassette players (car and otherwise) there is a small pin-hole which you push a needle in to manually eject a stuck tape. I remember many years ago, I ejected a tape which had gotten stuck. Somehow, I pushed the little lever behind too hard in the wrong direction only to twist is a little bit so it didn't return to the front properly. Whenever a tape was put in, it would immediately get rejected.

Cassettes are notorious for sticking especially cheap makes and anything over C90's. Insert a Bic type pen into the spool centre and turn the spools both ways to loosen the tape whilst keeping a bit of pressure on the other spool so the tape isn't slack inside the case. Then try fast forward/rewind the complete tape. As TF says try a tape cleaner but these are abrasive so use sparingly. A cotton wool bud and correct type of alcohol based cleaner(Maplins)can be used to clean the heads, capstan and rollers. Use a pen torch to look inside the cassette drawer to make sure there's no muck or broken bits of tape snarled up and jamming the mechanism.

Join the revolution instead......use a cd ;-)