Complex sentence: British Car Auctions is one of the main auto auction companies in the UK; however, there are a wealth of other national auto auctions, including Manheim Auctions and Aston Barclay, as well as many smaller, locally based auction centres.
Split into simpler sentences: British Car Auctions is one of the main auto auction companies in the UK. Other national auto auctions include Manheim Auctions and Aston Barclay, in addition to many smaller, locally-based auction centres.