Complex sentence: Dunning later moved on to New York working on UPA's "The Gerald McBoing-Boing Show" and in 1956 he moved to England to manage UPA's new London office.
Split into simpler sentences: Dunning later moved on to New York working on UPA's "The Gerald McBoing-Boing Show". In 1956 he moved to England to manage UPA's new London office.