Halls were regularish at Victoria in the late 50s early 60s I understand, especially on summer Saturdays. Up until the line was downgraded by the dark side most loco changes would have been done at Leicester where the main GC passenger depot was. Then on 'reorganisation' Annesley took on passenger work. Summer Saturdays were famous all over the country for unusual locos being turned out for passenger work. There is, of course, the famous episode of the 9F doing 90 down Stoke bank on the ECML.
The GC was also using 9Fs on passenger work, there is a recording on the Peter Handford 'Great Central' album (I think) of a 9F tearing through somewhere towards the southern end of the line, maybe Princes Risborough.
Anyway back to GWR locos, the Gas Works Railway as it was known to some GC staff, there is the well documented episode of a Grange arriving at either Leicester or Nottingham, details escapes me at the moment, and there being no relief engine available. The crew were persuaded to take it as far as Sheffield, where another loco was promised. On arrival at Sheffield still no relieving loco but the driver refused to take it any further, remember that the GC was built with rather more generous clearances than other lines. An inspector apparently agreed to take the loco forward but was stopped at Huddersfield, the loco cylinder having hit the platform at Denby Dale I believe. The loco was then impounded until a means of getting it home was decided. It made it's way home light engine, apparently very slowly in places.