LNER 225s - The answer is yes, as DanNCL sys above there is more demand than pre - pandemic.
XC HST's - I a possibility of the Avanti Voyagers going to XC, if there is enough requirement for paired up Voyagers to continue. If the demand is not there and not predicted to be there in say the next 10 - 15 years, then I can the XC existing Voyager fleet replacing them. The other option for replacing the XC HST's is the the EMT class 222 units, which along with the EMT class 180's I would say are also at risk.
Chiltern loco hauled - I can see Chiltern either having EMT class 180's or sharing some of the class 222 fleet with another operator.
807s - I cannot see the 807's going anywhere but Avanti to replace the Voyagers doing services like Euston - Birmingham which is all under the wires, which would replace the need for running diesel trains under the wires on the WCML. Avanti only have 18 Voyagers, there is only 13 class 805 units being built and there is at least 4 services a day with two of those Voyagers coupled together on each service. Now, admittedly it, may seem like a reduction but the IET coaches are longer, so a 7 coach IET would be the same length as to two 5 car Voyagers. If you look at the Avanti services from/to Glasgow Central there is a lot of cancelled services. Many of these cancellations, I believe are with not having the stock available to run these services. So 4 or 5 of the remaining class 807 would fill that gap. You also have to bear in mind that the class 390's are going through a refurbishment program, that will likely take the next 2 years or more. With the class 805 and 807 units, it gives Avanti the ability to have a more than adequate fleet to cover for these class 390 refurbishments and hopefully provide the full service required.
155s/156s/319s - Okay, with regards to Northern 7 class 155, 56 class 156 and 12 class 319 units, I can see these possibly being replaced by either more class 195/331 units being built or possibly a hybrid class 195/331 fleet with either three or four carriages per unit similar to what Greater Anglia have with the class 755 units.
The class 156 units with EMT are being replaced by class 170 units from TFW and Southern. These class 156 units are then transferring to Northern.
171 - This is slowly becoming a micro fleet, with previous units in the fleet being converted back to be class 170 units. As per the future comment on the class 171 wiki page:
As at August 2022, Southern operated 20 sets; 12 two-carriage sets and eight four-carriage sets. In September 2022 the two Class 171/2 and two Class 171/4 sets were reformed back into their original three carriage formations, returned to
Eversholt Rail Group and leased to
East Midlands Railway (EMR). Three moved to EMR where they will be converted back to
Class 170s while the fourth will remain on sub-lease with Southern. Further reshuffling will result in Southern having a fleet of four two-carriage and 13 three-carriage sets by December 2022.
[7][8][9]
In September 2022, 171202, 171401 and 171402 were transferred to
East Midlands Railway and renumbered to 170422, 170423 and 170424 before being renumbered to Class 170s/9s.
175s - As has been mentioned I can see these going either to GWR to replace their HST fleet or Chiltern to replace their loco hauled fleet. However, I think that there is too many in the class 175 fleet to replace the Chiltern Loco-Hauled fleet. The problem that you have is that if the class 175's go to Chiltern, then they are likely only to be using the 16 3 car units, as two of those coupled together would be the equivalent of the 6 coaches per loco hauled unit currently being operated. They would be no need for the two car units. However, if the class 175 went to GWR they could replace most of the class 255 castle units with using 11 of the three car units, with the 11 2 car units. You could two sets of two three car class 175 units working with each other to form 6 car trains and have a three car set as spare. But some of this has been mentioned in the class 175 speculation thread.
180s - The units with EMT I know are being held on for a few years, while class 810 are being introduced. But come 2025, I suspect that these will either go to Grand Central as there is only four units and one of those units I believe is still a four car unit? But it will depend on whether Grand central within the next two years plans to replace their existing class 180 fleet with new trains and perhaps buy brand new IET trains off the shelf?
222s - I am not sure where these could possibly go to be honest, other than being used on the Grand Central London Paddington - Swansea service. Even though Cross Country have an option on them, I suspect that they will not use them as they are not compatible with either the class 220 or 221 units. With the Avanti class 221 units becoming available soon, I would suspect that they are more likely to go for those as they can work with their existing fleet with little alteration (i.e. turning the tilt mechanism off). The only possibility would be if these went to Scotrail to replace twenty six HST sets.
230 - Even though the manufacture Vivarail has gone out of business, I am not sure that this has had any effect on the maintenance part of the company that would help with maintaining the units.
319s - The only other operator of the class 319 other than Northern is West Midlands Trains (London North Western Railway), who will be replacing their class 319 trains, along with the class 350/2 units with class 730 trains within the next year. Other than scrap, the only other option for these trains is to be converted into freight units if the demand is there though.
323s - Most of the class 323 fleet with West Midland Trains will go to Northern once replaced by class 730 units.
379s - Other than being converted to Battery - Electric units, I cannot see where this fleet of 30 units can fit in other than perhaps replacing the class 387/1 units at Great Northern, so that those can go south to Southern. The only other hope, would be replacing units in Scotland with work being done to electrify routes and possibly using the battery tech on some of those routes. But there is already a thread on this subject.
769s - This has been discussed in the 769 thread, but should GWR be able to get their class 769 units to work within the next year, then I can possibly see them taking the TFW class 769 units when no longer required. The problem, I think is that other than the Gatwick/Redhill - Reading services and perhaps the Didcot - Oxford shuttles, Slough to Windsor & Eton Central, Twyford to Henley on Thames would be the only services that they would be any good on. The West Ealing to Greenford and Maidenhead to marlow would be better done with something like class 230 units.