I agree I was disapointed booked a trip to York on Trainline.com, got an east coast HST going up and a Grand Central comming back, I wanted a ride on a MK4 set seemed a waste of all that money in the knitting
To be fair there is a good chance that the East COast HST came from North of Edinburgh and the Grand Central HST serves non-electrified lines and the 'DC' overhead electrified station at Sunderland.
....My proposal is, I think, quite simple. Set a date - say 2017 - after which if a TOC wants to run a service which is end-to-end under the wires (or beside the 3rd rail), and uses a diesel, an automatic £5000 fine is levied. Fair?
Not really. Essentially, the DfT decides who has what stock, okay, that's over simplifying, but if a TOC wants new trains it has to talk to them. But even if you exclude the services that have to run under the wires because of the DfT, you still get quite a complex situation.
You see, AIUI (and again I might be over simplifying), TOCs get fined if they cancel trains and they get fined if they run late, and at a particular point cancelling becomes cheaper then running late. So a late running diesel under the wires service is more likely to be cancelled on financial grounds if a fine were introduced, and, imo, that is counter-productive.