If I study pre-law in England, will it help me or hurt me with my chances of getting into law school?

It shouldn't hurt your chances for law school at all. In fact, if you came become a licensed barrister in England that route might be cheaper and faster than becoming an attorney in the United States. You would then be able to sit for the bar exam in a U.S. jurisdiction as a foreign educated lawyer. If this is an option for you and you know that you're like to be an attorney this is a career route I would certainly consider.