There is nearly no difference between PC and Standard. The only difference being the seats are all around tables and the anti-massacres. It has improved slightly with the long-drawn out recovering of the seats to a maroon leather.
The Premier Class accomodation isn't going, just the sets shortened to 4pce. 224XX and 225XX being taken out due to the electrical consumption of the A1 cars
29000's or C3K's have often done Enterprise workings. Back in the day, either 2xBaby's replaced the dead loco or, if the failure was in Northern Ireland, sometimes a '80' Class.