The cars were sold in the UK but I'm not aware of shop manuals published in English. In fact I think it's only in the US that by law the manufacturer has to make service manuals available to the public. You can try the folks at Haynes Publishing to see if they plan a shop manual for the 380-420-500-560 SLs. There is one for the 350-450 SLs.

Try also purveyors of automobile literature such as Barry Schiff if he's still in business. Such folks have manuals from around the world. But from the number of respondents in Europe looking for manuals in the US, there's not a great supply.

Sixto
95 S420
87 300SDL
83 300SD