Ascott delays aren't entirely up trains, because of the way the section to Moreton is signalled, or rather, not signalled.
Once you're past the home signal just inside the start of the double track, that's it in terms of block signals as far as Moreton, so if two down trains are chasing each other, eg the 17.51 to Worcester is following a badly delayed 17.21 to Hereford, it has to wait at Ascott until the 17.21 is safely inside the outer home signal at Moreton. With the 18.21 to Hereford not far behind, this can also pick up delay minutes at Ascott if this scenario arises.
There are signals between Shipton and Kingham to protect Bruern level crossing, but they do not act as block signals.
I would have though a a half to a mile of double track from the junction would enable Down trains to clear the Banbury line]I would have though a a half to a mile of double track from the junction would enable Down trains to clear the Banbury line
But as I have noted previously, Network Rail won't do this, because it would involve interfering with the signalling set-up at Oxford - due for replacement 2014-15 - cost far too much money for such a short lifespan and also make the redoubling scheme too expensive.
Hence the plan to bring the freight loops north of Oxford up to passenger standard, which would allow Cotswold trains to clear platform 2 if a delay is anticipated on the single line by moving them into the down loop, so keeping them out of the way of services heading to Banbury, but also move them part of the way to Wolvercot (the railway still uses 19th century spelling) junction. But this will involve a bit of work. I can remember a ride over this track in a Turbo a while back when the point to the main line at the north end of platform 2 had jammed. Even at low speed it was lively.