Free jazz is a big topic, and "Webern-ish" restricts it a lot. There have been a lot of good suggestions, mainly for US artists, so let me suggest a few European things. Since you like Evan Parker, try the Schlippenbach trio's "Elf Bagatellen". It's Alexander von Schlippenbach on piano, parker on saxophones, and Paul Lovens on percussion. It's probably the most Webern-ish "jazz" recording that I have. It's FMP (Free Music Productions) CD 27.
Parker also played in the London Jazz Composers' Orchestra. They have a number of recordings out. It's a much larger ensemble, and involves an interesting mix of composed material and free improvisation. Most of what I've heard has been interesting; I don't have a particular recording to recommend.
Anthony Braxton has a formalist side while still allowing for free improvisation. His compositions are weirdly notated. I like some of his live quartet recordings especially. The Dortmund (Quartet) 1976 with George Lewis (trombone), Dave Holland (bass), and Barry Altschul (drums & percussion) is one I have a copy of and would recommend (hat ART CD 6075). I also like (though don't have a copy of) a 4-disk set of the quartet with Marilyn Crispell (piano), Mark Dresser (bass), and Gerry Hemingway (drums) recorded in a German city I forget at the moment and also released on hat ART.
I've heard a couple of interesting concerts in the last couple of years and can recommend some performers, though I don't know recordings. Mark Feldman, a violinist and former Nashville studio musician, is married to Sylvie Courvoisier, a pianist, and they play free music together. It's more in the European vein. They've also recorded together. I also heard Sylvie play duets with Ellery Eskelin; I'm truly sorry that concert wasn't recorded.
Sticking with European artists, Gerhard Ullmann is a clarinetist who leads a clarinet trio. They gave the only out jazz performance I've ever been to where they kept all the "moldy figs" in the audience for the entire concert. Quite entertaining performers as well as virtuosos.
That's barely scratching the surface of a small sector of free jazz/creative improvised music.
-- SG (listening to the late, great Julius Hemphill's "The Hard Blues" from the album now titled "Reflections" as I type - one of my favorite treatments of the blues.)