Find another dealer!!
A reputable independant dealer will probably be more willing to spend the time DIAGNOSING and fixing the car. Receiver replaced 3 times in 12 months? I'm guessing they haven't been finding/looking for the root of the problem...

Whereabouts are you? England?

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190E's:
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black 2nd owner
http://www.maylane.demon.co.uk/190esmall.jpghttp://www.maylane.demon.co.uk/190esmall2.jpg