I thought that GWR were planning 2 trains per hour on the Cotswolds line (1 stopping and 1 semi-fast), if this did happen then at least one end would have to be redoubled in order to operate a reliable service.
A taskforce involving the rail industry, local authorities and user groups is due to report any time now on proposals for the future development of the route, But without more double track at the Oxford end of the line and on the section between Worcester and Evesham, is is simply not possible to run a robust 2 trains per hour service - and that assumes it would wash its face financially, as loadings west of Moreton-in-Marsh are far lower than to the east.
There's a de-facto 2tph in the peaks, as some of the Oxford terminators are extended to Moreton-in-Marsh.
Up to a point. In the mornings it is only in the direction of Oxford, while the afternoon service requires some very punctual running all round in both directions to get trains through between Charlbury and Oxford without mayhem ensuing.
IETs certainly help in this respect. The 17.38 from Moreton-in-Marsh had hardly ever left on time from the day it first appeared in the timetable, due to delays on the outbound run as the 15.50 from Paddington when it was an HST - slam doors being the key bugbear. The instant an IET took over, it started to reach Moreton-in-Marsh on time or just after (despite a couple of current temporary speed restrictions between Shipton and Moreton-in-Marsh) and on time departures back to London are pretty much guaranteed now.
Could this not happen all day as the line south of Moreton-in-Marsh always seams to be busy, especially when 5 carriage class 800's operate the services
No, the infrastructure can't handle 2tph reliably with any margin for late running. When the Wilderness Festival is taking place at Charlbury in the summer, GWR does extend some Oxford terminators out to Moreton-in-Marsh to boost capacity, but the service has usually fallen apart at some point in the day due to late running - it may work better in future if IETs are being used, with their better acceleration easing issues with late running and single-line occupancy, but as things stand it is simply not a sustainable proposition on a regular basis.
In my humble opinion the line from Oxford to Hereford should be doubled throughout. The line should be resignalled and upgraded to allow for faster speeds and more frequent trains. The line has seen significant growth but has seen very little in the way of upgrades.
Bit hard to redouble the tunnels at Ledbury and Colwall, as they both have single-track bores.
I don't know how much faster you think it should be. Oxford to Ascott-under-Wychwood is 100mph, Shipton to Moreton-in-Marsh 90mph, Moreton-Evesham 75mph (could be mostly made up to 90mph without much trouble but Aston Magna curve is a permanent 60mph limit and won't change) and it's mostly 90-95mph from Evesham to Worcester. With all the station stops along the way, there would be little to be gained by increasing speed limits except perhaps Moreton-Evesham. I don't know what the ruling limit is Ledbury to Hereford but that's the only other place any changes would be possible, given the limitations imposed by getting through the Malvern hills and negotiating Worcester.
Some additional track was provided between Oxford and Worcester, but the line is by no means double track throughout, not does it need to be. Part of the problem accommodating more services at some of the smaller stations at the east end of the route over and above the single parliamentary in each direction they receive today is that they are located on the remaining single track section, which clearly extends the occupancy of journeys that call, but providing a second platform and appropriate access routes would be prohibitively expensive at ALL of Hanborough, Combe and Finstock stations. Extending double track from Oxford out as far as Hanborough would be a very useful compromise. A double track station layout for the main line could be built at Hanborough with an additional bay at the east or a west end turnback siding provided. That would provide capacity for better local services as far as Hanborough, and flexibility and resilience for all Cotswold services. Shortening of the single line might also allow a handful of additional daily calls at Combe and Finstock, but I don't think a regular interval all day service would ever be justified at these stations. If full doubling throughout this section is ever proposed some long term value decision needs to be made regarding the minor stops. Some more frequent local buses serving the area and offering guaranteed connections with trains at Hanborough or Charlbury could serve far more people far better than the current very poor rail offering.
Some? 15 miles more in both directions to give 32 miles of double track in the middle of the line, leaving single-track sections roughly nine miles each at the ends.
While Finstock and Combe would probably bite the dust in the event of full redoubling - and no one would ever suggest more frequent calls as the two stations are a long way from the places they purport to serve - in the case of Combe there already is an hourly bus service through the village to and from Oxford most of the day. Anyone in Finstock who wants more choice of trains will go to Charlbury anyway.
I have no idea why on earth you make the claim that it would be prohibitively expensive to reopen the second platform at Hanborough - though you then go on to almost immediately contradict yourself. Much of the existing disused structure could probably be brought back to life quite easily looking at its current condition (and it was inspected only last year as part of the taskforce's work I mentioned above and other work being done by Oxfordshire County Council on transport provision around Oxford). An extension has just been provided on the existing platform that more than doubled its length.
Where would the parking go? On google it looks like they are building houses in the most obvious place for a big car park....
For starters you could add a Chiltern-style steel deck on part of the existing main car park (ie the one off Main Road, which is on higher ground above the station, not the limited spaces that can be seen from trains - Google's satellite appears to have passed overhead on a Sunday, so there are hardly any cars in the big car park).
The housing site south of the railway was designed to allow for car parking for rail passengers - lots of it, all along the boundary with the railway cutting, and there is also land set aside opposite the station that could be used for a station building and a car and bus drop-off/pick-up too. There is a site plan at the end of this travel plan prepared by the developers showing an indicative layout for the car parking, with the white area between set aside for turning space/future staton facilities. Whether any section 106 planning gain money has been set aside from this and other developments around Hanborough to pay for the car park etc, I don't know.
https://publicaccess.westoxon.gov.u...f/18_00307_CND-REVISED_TRAVEL_PLAN-620184.pdf