Other than the 442's, I think I'm correct in saying that the last stock built with compartments were the Mk2 BFK's in the mid 1970's. BR policy was to dispense with compartments.
Correct, the last loco-hauled corridor stock were Mk 2 BFKs, specifically Mk 2D (so air conditioned, which was considered even better by users because of better sound proofing). There were also Mk 2D FKs, many of which were in use on CrossCountry services by the late 1980s.
Then NSE came along and for the 442s brought back First Class compartments. I'm guessing that because unlike with loco hauled stock (or HSTs) where first class could be put at one end of the train, through-gangwayed multiple unit stock had it spread across the train and it gave greater privacy when Standard Class passengers were walking through a train (or even standing in the peaks).
The 442s had six compartments (so 36 seats in all), and then a small open saloon of 14 seats arranged 2+2. This latter area was originally Standard Class but greater than expected demand for First Class saw it become First Class too. It was popular with those customers wanting a table.
Interestingly, if the Class 471 Networker Express for the Kent Coast services had been built after the 465/466 Kent Link commuter stock, that too would have had First Class compartments based on mock-ups displayed by NSE at the time.
https://en.wikipedia.org/wiki/Briti...381_and_471#/media/File:Class471MockUp002.jpg
https://en.wikipedia.org/wiki/Briti...381_and_471#/media/File:Class471MockUp003.jpg
Before the 442s were taken off lease with SWT as a result of the 2007 franchise award it was being looked at to remove the compartments anyway as part of a major interior refurbishment.
Interestingly, whilst a lot of people here seem to like the idea of compartment stock coming back I wonder just how many First Class passengers would appreciate it? The one thing you don't have is a table (fixed of fold down) and you just have to look how many First Class passengers on SWT in the peaks are business types working on their laptops or working on papers. Plus it is not unusual on peak trains for the single seats to fill up first because people prefer not to have somebody sitting next to them.