Other than the daytime Sunday one the other Penzance extensions would otherwise just go onto Laira.Personally I'd bin the Penzance stuff, even though it is fairly well used, for now at least if it meant we could have additional 8 or 9 car trains north of Plymouth. 4 and 5 car trains on many services simply won't cut it, especially May to September and all school holiday times. XC travel is about to get a whole lot more grim.......
From what I can see the following will be double sets on weekdays as they split/join during the day. Hopefully there are others:
0620 Plymouth - Edinburgh might detach at Bristol for the 0900 to Manchester?
0628 Penzance - Edinburgh from Plymouth
1807 Edinburgh - Birmingham
0543 Leeds - Edinburgh
1003 Edinburgh - Penzance until Plymouth
0703 Birmingham - Edinburgh
1305 Edinburgh - Plymouth until Gloucester
0635 Bristol - Edinburgh
1403 Edinburgh - Plymouth until Bristol