Complex sentence: He was a contributor to the Omega Workshops, but was one of those breaking away with Wyndham Lewis; this breakaway began the Rebel Art Centre, with the Rebel Art Movement, somewhat akin to the Dadaists in Paris.
Split into simpler sentences: He was a contributor to the Omega Workshops, but was one of those breaking away with Wyndham Lewis. Which began the Rebel Art Centre, with the Rebel Art Movement, somewhat akin to the Dadaists in Paris.