Complex sentence: Citibus operated in the 1980's around the Greater Manchester area, they mainly operated on the North side of Manchester based around their Chadderton base, they generally copied routes run by Gm Buses and ran a small number of very old buses.
Split into simpler sentences: Citibus operated in the 1980's around the Greater Manchester area. They generally copied routes run by GM Buses and ran a small number of very old buses.