bhodges, I wouldn't have thought "Feldman" about any of Furrer's music, so perhaps that's not representative. Of course, Feldman wrote a lot of different stuff. I don't think "Feldman" even about some of Morton's own output! Well, not without some serious pondering, anyway.
Dundonnell, I'm not sure I can help you in your quest. I know and like the people you've mentioned, but probably the other ones I know and like are going to be along the lines of those "avant-garde fashions" you alluded to. But on the Wikipedia list, I know the music of Paul Giger, some of which I like very much, some not so, so I'm probably not a good guide for that. Heinz Holliger and Klaus Huber have written some very substantial music, good and solid I would say, though those two, especially Huber, are very definitely European avant-garde. At least so I would guess. I'm afraid I don't pay much attention to "fashions" as such. I just like listening to good music. And Huber has written some very good music indeed. Not all that easy to get a hold of. I have two cds of only Huber, and a handful of Huber pieces scattered about on other CDs, mostly on those Donaueschingen collections. The Furrer I have on right now (Nuun, on Kairos--the other Kairos disc) is starting to sound more and more like Huber! (Started out vaguely reminiscent of some New York folk--the Bang on a Can folk, but only vaguely.) I'd say edward's reference to Nono is probably spot on.
One of my favorite Swiss composers, though, as far as I know (as I don't pay much attention to nationalities, either, I'm afraid), is Rainer Boesch, who's also a very nice person, too. Not that composers need to do anything beyond writing good music..., but still. Boesch isn't on the Wiki list. Wikipedia lists often side-step the electroacoustic crowd entirely. I guess their compilers are still of the "music is what you make with violins and pianos not tape recorders and laptops" school of thought. Pity. Means their lists never include some of the more interesting and provocative composers of the past sixty years. (1947 is the first "tape" piece, by Pierre Schaeffer. Not the first electronic music by any means. Some electronic instruments date from the 19th century already.)
So this would be my Swiss short list:
Rainer Boesch
Klaus Huber
Beat Furrer
Heinz Holliger
Paul Giger
Voice Crack (a turntable, live electronics group)