I can assure you that drivers are NEVER informed of declassification..ever..its just a passenger myth that came from"first class doesnt apply on sundays"
As for unit substitutes..I dont believe that entitles you to first class if standard is empty...again,not sure!
I've never heard the 'first class doesn't apply on Sunday' thing before!
As you're a GN driver, I can say that the service in the morning that form the 0818, 0846, 0902 and 0943 from Hatfield are all declassified. They'll be 4 or 8-car in most cases. There are others, booked as 6-car, which could be changed and thus allow you to sit in first class.
In the evening peaks from King's Cross, the xx27 and xx57 will usually be a 6-car 313 (there's one specifically booked as 4-car though), but sometimes they are substituted for a 4-car 317 or 365 - for whatever reason (you'd know more than me!). In these cases, there's NO first class on that service. Now if a driver, RPI or platform staff don't want to tell people then so be it (good for me!) but it WILL be declassified!
I don't remember when it was (over a year ago), but FCC did try putting up signs to say that the first class section was declassified - but I guess it was a nightmare. Who puts them up, who takes then down etc.
I think the plan is to get more 313s and add more services in and out of Moorgate, with 321s replacing the 313s from King's Cross - which will either mean every service offering first class, or FCC being able to reintroduce first class operation on them at all times (which will be bad for me!!).
I always book a table seat on VT services and during the peaks it is unusual for the other three seats not to be occupied. You have to bear in mind that IMO a lot of people travelling in the peaks are individuals, it is not selfish and arrogant at all to want a table seat (especially laptop users who want a plug)
Of course it's fine to take a table! I think it's a bit different if someone takes a table and then tries to put others off by spreading stuff around - coats and bags on the other three seats.
THAT is selfish, but totally different.