well i figured it out! well not me, i went a radio guy (and he said the same thing as you as it appears!)
the little switch in the dash for the speaker allocation, was interferring with the output, apparently dragging it to earth!
still no cruise control though haha. i guess you cant have everything. if thats the only thing wrong with the car i can live.
where is the little accutator thing on the pedal though? i cant see anything so im thinking it may be missing :S
thanks a million for your help guys, its very valuable knowledge here! XD

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1971 280SE - The S Class
1974 280CE - Sterling
1988 300E - Stanley