Complex sentence: Robson & Jerome would eventually sell 7 million copies of the albums released, and 5 million copies of the 3 singles released before they decided to quit, despite being offered £3 million for a third album by Cowell.
Split into simpler sentences: Robson & Jerome would eventually sell 7 million copies of the albums released, and 5 million copies of the 3 singles released. They decided to quit despite being offered £3 million for a third album by Cowell.