i just checked out your mix. you do indeed have an expansive definition of the genre! i knew most of these already, but a few were new. Terranova especially impressed me, i'll have to track them down later
now that you've thrown together that eschewed the usual, perhaps you could list what you consider to be the usual? you mention Massive attack, Portishead, Tricky. those are definitely the big three. but who else?
i've never liked putting DJ Shadow in there, his stuff is more ambient breaks than trip hop. that UNKLE track you chose is good here, but most of theirs is not.
what about something like Hooverphonic? some of their tracks definitely fit (like 2Wicky), but others are very much upbeat and cheerful. what about Everything But the Girl (there last 2 at least)? Morcheeba?
wikipedia even lists Bjork and Gorillaz as trip hop!
this is definitely the genre that gives me the biggest headache when i'm tagging new music...