Aren't some of the 387s that have gone to GWR not meant to be staying? I'm out of the loop with the /2s and /3s, but weren't at least some of the /3s staying on the Western and are not all the /2s gone from there? Which would mean the numbers in the post summarising what should be moving around will be lower.
I would also concur with those suggesting that the 455s get put into store to begin with, just in case of sudden spikes in passenger numbers when the weather improves, when people decide they've had enough of being indoors during the winter and want to go back to 'normal'. It certainly would not hurt to keep at least some ready to go, just in case, for a short time to see if humanity does what it does best, that is the unexpected.
Of course, I still expect all will be fine and good, those who know what they're doing with timetables, modelling and so on at GTR have no doubt factored this in when making their decisions. I'd also like to add that, while I'd look to keeping a handful of 455s ready for crowd-busting purposes this summer, that if I had the opportunity to effectively have a spring clean of the fleet, to bring it a bit more up to date, then I'd be doing so post-haste!
Cutting back the Southern service to MKC, well I can see why it would be done. It only makes sense, and I confess I've only been on one 377/7 north of London years ago so I have only one piece of anecdotal evidence, based on what I saw when I used the service. On my one use of it, this would have been in the early to mid afternoon from memory, out of MKC it was a pretty quiet train. It didn't really get all that busy until we approached places like Watford and by Harrow & Wealdstone it got much busier.
Which makes sense as it is a very useful route, but beyond Watford Junction I would permanently axe it too. Of course, this would not allow for peak time variations, but given what I've seen of the peak it's just not the same anyway.
Which leads me somewhat onto an important question. If the 455s went into short term store, where would have sufficient room for a decent size number of them?