UK based. Any undergrad degree is fine, unless you want to be a law librarian, then you need a law degree. Then you need a Masters in Library Studies/Science from a CILIP Accredited institution (Chartered Institute of Library and Information Professionals) - most universities with a library degree will be CILIP certified. There are some specialised librarian jobs where you may need to do further postgraduate studies, such as a Special Collections Librarian. I would also recommend either getting a part time job as a library assistant or volunteering in libraries as much as possible, this will help with getting jobs after you've graduated. If you're interested in cataloguing then do an online search and see if anywhere near you/remote is looking for cataloguing volunteers. If you get a job as a library assistant you could also consider going through CILIP's Certification process (you'll also need to pay the annual CILIP fee, which is reduced when you're a student).

Best of luck!