It's been a few months so I've gone through it this evening and made some updates. Some of this is based on logic and the passage of time, and some from details helpfully passed on to me from others, so as always please let me know if I've made any mistakes - and thank you to all who help keep this list going.
The changes I've made are as follows:
Chiltern - added MKV DT training to Stourbridge and Marylebone depots.
Great Northern - changed 379 from training to in service for all depots that I understand will sign them (Cambridge, Hitchin, Hornsey (link dependant), Kings Cross, Kings Lynn and Peterborough)
GWR - added Bristol to Exeter for Paddington GWR (thank you
@800301 ) . Added Bristol Parkway to Bristol TM for Worcester GWR (thank you
@class ep-09 )
Northern - changed 323 from training to in service for Buxton. Changed 333 from training to in service for Doncaster
Scotrail - added in details for new depot at Millerhill
Thameslink - changed "soon to learn" to currently signing St Pancras - Welwyn Garden City for Ashford
Transport for Wales - added 756 to "training to start soon" for Cardiff Mainline, changed "route learning soon" to currently signing Central Rivers TMD for Crewe, deleted Tyseley TMD for Shrewsbury
West Midlands Trains - added 730 to Coventry