It's probable only a minor thing, but could the autumn weather be more of an issue on the WCML than the ECML, given how flat the ECML is (IIRC the highest part on the Kings Cross - Waverley service is Grantshouse, which is hardly mountainous, whereas the WCML trains have to negotiate Shap and Beattock), so any slippery conditions are less likely to impact upon the ECML?
Plus we've done a few things recently to improve reliability of fast ECML services (e.g. the Sheffield - Scunthorpe stopper was chopped at Doncaster so that's two fewer services crossing the main line on the flat, all the money spent at Kings Cross)?
London - Glasgow is a longer journey too (approx five hours versus approx four hours to Edinburgh) so more scope to be delayed by five minutes?
Or just coincidence - any two lines will have slightly different stats, it may be nothing to do with the operator or the trains but just a couple of delays will skew the figures a little bit, dunno!
How it always used to be done. Separate Glasgow-Birmingham (two-hourly, whatever) and Birmingham-London (every 20 minutes) services
The two problems there would be:
1. Is there a spare path for an hourly New Street - Wolves service (since the VT changes meant that they went from running an hourly London - New Street - Wolves service and an hourly New Street - Wolves - Scotland service into one combined train, but I don't know that the path remains to permit these to run separately) - unless you're suggesting no through trains from the Black Country/ Wolverhampton to London?
2. Is there room at New Street for a Scottish service to lay over (previously these WCML services ran through to Bristol etc, before being linked to the Euston service instead - platforms in Birmingham are at a premium - hence Wales'n'Borders running through to International rather than blocking a New Street platform for ages - so what do you do with the Scottish trains when it arrives at Birmingham?