Complex sentence: Horace Parker (Hawtrey) is a wealthy young man who is exceedingly selfish and self-centred: not only is he a miser, but he also expects his friends (and everyone else) to conduct their lives according to his personal convenience.
Split into simpler sentences: Horace Parker (Hawtrey) is a wealthy young man who is exceedingly selfish and self-centered. Not only is he a miser, but he also expects his friends (and everyone else) to conduct their lives according to his personal convenience.