>terminals and PCs w(h)ere common in 1983
No they weren't.
The IBM PC was introduced in 1981. You couldn't do much with it, certainly not much related to mainframe programming. They were very expensive for what they did. Minicomputers existed, but they also didn't cross over mainframe territory.
People with heavy data processing requirements were mostly using DOS/VSE on S/370 and 4300 mainframes. No timesharing in DOS. It was still extremely common in industry to have people sitting with coding forms that were then passed to data preparation teams for punching. I've sat with teams painstakingly writing DOS JCL onto coding sheets.
If you were a larger user that could justify the investment in MVS, you could potentially use the Time Sharing Option, an interactive environment with a reputation for being cumbersome and inefficient - you'd only extend the "luxury "of using it to a comparatively few select people.
Computer time was also extremely expensive. Cambridge University wrote their own version of timesharing (http://en.wikipedia.org/wiki/Phoenix_%28computer%29) for their (early) S/370 in order to support a larger number of users and time on it was still so restricted that usage was "priced" to reflect demand at different times of day and CS students would either have to work at 3am or make extensive use of cards or other offline data entry to get their projects completed within the allocated budget.
Whereas there were minicomputers and early personal computers around, they were scarcely to be seen in what was still the predominant environment of the computer industry - the (IBM) mainframe shop.
Actually, the British government tended to prefer homegrown procurement and more of its staff were likely to be working with George 3 (http://en.wikipedia.org/wiki/GEORGE_%28operating_system%29), which had a far better interactive environment than IBM offered.