The Library building lived off up the road to Skinners. Prior to its erection in the mid 1980s, the library was housed in the Admin Block in a room directly below the Staff Room. For a period, this old library coexisted with the new Study Centre, being used as a resource for English and General Studies lessons. Careers info and university prospectuses were also kept down there before later moving to a room in the north-west corner of the new building. By the 1990s, the old library had become the 6th Form Study.
The new Library was managed by Mr Smith, and operated by Mrs Gyle (and later Mrs Hennell). It was originally run using a traditional card and envelope system, with books being stamped out, but this was replaced with a flash electronic system in 1992/3. Each pupil was allocated a laminated card with a number and a barcode on it, and this was used to check books out. The hardware consisted of an Acorn Archimedes with an IR scanner. In the mid-'90s, this system was replaced with a different set-up (probably involving a PC), but in order to take advantage of the new set-up, pupils had to re-register at the library. Most people im my year didn't seem to bother.
With the re-designation of the Admin Block study-room (the old library) as a Language lab (after the Lower School fire), the Library became a popular place for 6th Formers to do homework and "hang out" as it were. The 6th Form Base was generally seen as a little cliquey and too noisy for such things.
Following the re-building of Lower School, the Library was converted into PE classrooms, PE1-3. Previously, A-level PE had been taught in any old room that was free (often the westernmost English Terrapins). The library was relocated to its old home in the Admin Block, but extended into the former Special Needs classroom to the north so as to cover most of the Admin Block floor-space.
The 2001 Ofsted report welcomed the move of the library to a central location, but criticised the range of books and resources. It also suggested that the new library was physically too small. I don't know whether the library occupied the full space of the Admin Block's ground floor at that point. It is possible that it was only in the study room, and didn't cannibalise the Special Needs room until later. Was it?
Thanks to Jules for pre-'90s info.