�Judicial Officer� is a general term and its definition can vary depending upon the context. It can include judges, district judges and sometimes lay magistrates.
I have not heard the term �Regional Magistrate� used in England. There are District Judges, and these sit in magistrates� courts. They are legally qualified and sit alone (in contrast to "lay" magistrates who almost always sit in a Bench of three). They hear cases that are proper to that court but that, for one reason or another, are not heard by lay magistrates. This might be because the case is expected to be exceptionally lengthy, or if it involves substantial issue of law. They used to be known as stipendiary magistrates.