As to the article "the", I've been bemused for a long time about how UKers will refer to "going to hospital" or "to university", without the use of the word "the". I used to find this strange.

NO!NO!NO!
"In hospital" and "In THE hospital" mean two completely different things.

"In Hospital" implies "is a patient", just as "at university" implies "is a student"
"In THE hospital" or "in THE university" merely describes the persons location, NOT his/ her activity.

eg "My mum is in THE hospital visiting my Gran"
or "Uncle Joe is in THE hospital. He has to carry out an emergency operation on a baby"
or Dad is at THE university today, he is re-tiling a roof there.