Complex sentence: He was dropped from the frontbench by William Hague, since when he has remained on the backbenches, and is seen as being a supporter of David Cameron whose constituency, Witney, is next to his in Oxfordshire.
Split into simpler sentences: He was dropped from the frontbench by William Hague and has since remained on the backbenches. He is seen as being a supporter of David Cameron whose constituency, Witney, is next to his in Oxfordshire.