Stuart Zender left after reportedly being involved in a dispute about division of profits within the band. Nick Fyffe, his replacement (you can see him on their Live in Verona DVD, plus the Synkronized and Funk Odyssey album if I remember correctly) left after the Funk Odyssey tour for reasons unknown
AFAIK. The bulk of the basslines on the Dynamite album were recorded before Paul Turner got there, either by Rob Harris (guitar) or machine generated.