I think the GWR Paddington to Oxford service should be extended to Banbury.
At least then, there is the option of transferring to Chiltern for the onward journey to Birmingham.
Although GWR do operate to Banbury, it is only a two hourly service that starts at Didcot Parkway.
It also does not help on a Sunday when the service north in the Oxford direction is now only once an hour, from Reading - on both GWR and XC.
Both service leave the same time, or a minute apart in the hour, which is absurd.
They should be half an hour apart, in the hour.
An example for the 31st March, in the attached image.