Complex sentence: Moving to Bell Records, which had signed The Bay City Rollers, King was asked to produce their first release "Keep on Dancing", which reached number 9 in the UK charts; he had no further involvement with the band after that.
Split into simpler sentences: Moving to Bell Records, which had signed The Bay City Rollers, King was asked to produce their first release, "Keep on Dancing". It reached number 9 in the UK charts, but King had no further involvement with the band after that.