MCR247 is correct in everything he says.
It is not feasible to revert "a few diagrams" to locos + stock due to the slower top speed, and in particular on the Birmingham-Scotland services as it would simply not keep to time nor will it be able to go round corners as fast as 221s or 390s. You may be able to reduce the time deficit by short-forming, but then it would be as waste of time as you would be simply replacing a train of a similar capacity for a slower one.
And yes 15mins does make a difference - Eurostar shaved about 20mins off London-Paris/Brussels journey times when the first phase of HS1 opened which triggered an increase in passenger numbers.
The railway is not run for the benefit of trainspotters or for those who are stuck in the past, and some of the posters in this thread need a reality check.
I wanted to say something along the lines of that, but didn't know how...
In reality, the saved journey times for say - A Glaswegian working in Scotland, will be massive. If he made the journey daily, or even every three days, thats still (5 days - 2 and a half hours, 3 days - 90 minutes) cut off the time...
So thats quite a lot in that respect
? Wonderfully reliable train that.