Can anyone advise me on whether S35s will work ok on my Beocenter 1800?

Yes  - no problems at all. Check which sort of S35 it is though. The type 6311 had a rubber edged bass driver but the later Type 6316 had foam rolls which will be deteriorating now. If they have, they will need repairing. Worth checking the cross over at the same time if that is the case.

Thanks for the advice Peter, they are the 6311 rubber edeged drivers.

I just picked up a pair of S35s at a flea market for 10 euros. Type 6311, but they have foam surrounds, not rubber. Not rotten yet, but near enough.

Who can suggest a good (online) step-by-step guide to refoaming?

Or are these speakers worth the trouble?

Peter

Peter, try this:

http://www.goodhifi.com/

Pekka