Matlock played bass on Anarchy in the UK, I believe Jones did the bass on the rest of the album. You can tell the difference, Anarchy has a fluid bassline, all the other songs the bass more or less plays the root notes. If you listen to the sp$nk bootleg Matlock plays pretty tasty basslines on that.
As for Sid...if you watch any of the live shows with him it's obvious he is playing, just very badly, however It's also obvious he's pretty high as well.