In the case of Exeter to Plymouth/Penzance, it may well be that the sea wall section would make any scheme prohibitively expensive but the one that really seems to stand out is Worcester to Hereford.  Is there anything on this route which would make electrification difficult?

It does say though that as numbers recover, long distance operators will have more autonomy and commercial freedom (page 31).  It expands on this on page 58 by saying:

Only seven which are on the list but I have visited two which are now closed:  North Woolwich and Tilbury Riverside.

Considering much of Europe uses speed-based rather than route-based signalling, would there even have been an explicit route indication shown to the driver in this case?

3 is Glasgow Central.

The October 1975 Paddington Station Workings book shows the 2345 as having one SLC^▸ (Service Level Commitment) is the formation which was detached at Exeter along with a GUV (Cars).  I expect this sleeping coach was for the use of Motorail passengers travelling to Exeter.

Sorry, wasn't thinking about the journey planner.  Hopefully they will update this soon now they have published the timetables.

I can't see anything in timetable B1 showing the Melksham service as provisional only.

Timetables for 14 September to 12 December are now available on the GWR^▸ (Great Western Railway) website.  Looks fairly close to "normal" now with some notable exceptions (for example Paddington to Cardiff remaining hourly for most of the day).

28 is Taunton.  There are 5 others I can name.

https://www.youtube.com/watch?v=Nv43WftUSiM

Following the cab ride video of the first SuperFast Bristol to Paddington service last month, GWR^▸ (Great Western Railway) have now released a cab ride of an HST^▸ (High Speed Train) journey from Plymouth to Paddington on the last day in service (18 May 2019).  I will not comment on the journey (so as not to spoil the video for anyone) but will say that if you have the volume high for the engine sounds, you may want to turn it down when in a station since the buzzer is quite high pitched and loud.

I don't have the notice to hand, but seeing as Swindon PSB (and the associated Chippenham remoted interlocking) were not comissioned until 1968, presumably the new signals were initially controlled more locally (possibly by Thingley Junction)?

Chippenham would have been resignalled a little earlier than that (as part of the late 1960s Swindon MAS scheme).

https://www.youtube.com/watch?v=6SfwsH8QIrs

GWR^▸ (Great Western Railway) have released a cab ride video of the first SuperFast service to leave Temple Meads for London back in December (calling only at Parkway).

Newbury seems to have lost most direct services to and from London this week.  The GWR^▸ (Great Western Railway) site says that the hourly service will alternate between fast Reading to Taunton and calls at Newbury, Pewsey, Westbury and Castle Cary but all of the slow services before the 1504 off Paddington are first stop Pewsey after Reading.  In the up direction there are no calls between 0835 and 1935.  There is however hourly all stations shuttle is running between Reading and Bedwyn, hopefully no-one from Newbury is going to need to travel further west.  Maybe this has been done to try and discourage any non-essential trips to London and also to prevent overcrowding on HSS^▸ (High Speed Services)?