its quiet common for regional airports to close the doors over night between last flight and first flight in the morning. Some national airports do it as well eg Tallinn.
Its not the airports fault. In fact there is a link between airports having a reputation of being dirty and smelly that don't close for a few hours (when the place gets a good unrestricted wash down) and those that stay open with people everywhere.
What the UK is particularly poor for is public transport and timings. Most countries time the public transport runs for the airport time table. SO the first bus arrives say an hour before the first departure. And the last bus at 40 mins after the last arrival. UK they don't seem to give a toss when the first bus arrives or last bus departs.