I would have more sympathy if there weren't so many examples of a train packed to the rafters in standard whilst only half full in first. I've seen this happen a lot on the TPE trains, perhaps in such a situation it should be mandatory for the guard to open up first/declassify and let all passengers use all available space on the train.
Keep doing that and you can wave bye-bye to First Class revenue. Who would buy a First Class ticket if it's routinely opened up to Standard Class passengers?
Quite so. In the Cambridge example the passenger can still buy individual single tickets, on a graduated scale by stages, if they want to.
Yes, the tiers are basically:
-£1 (for City Centre - Station - Addenbrooke's journeys only)
-£2.80 for a "into city" journey from roughly the town area
-£3.30 for a longer or "cross-city" journey