Permitted Routes Gloucester to Canterbury

Looking for advice please, I am travelling from Gloucester to Canterbury this Sunday.
Assuming the usual cancellations due to shortage of train crew, on the Cheltenham to Paddington route, would the ticket be valid via Birmingham to Euston please?
My ticket is valid by any permitted route.
Thanks in advance.

Narional Rail Enquiries tells me not (ie it says multiple tickets required and doesn't quote the normal fare.
However your ticket would be valid via Bristol Parkway, which might be handy, and (at a guess) via Worcester and Oxford. Also into Waterloo, but they're on strike!

Ticket wouldn't be valid via Birmingham, unless specifically there is mutual ticket acceptance via Birmingham, usually this is posted on NRE or GWR websites.

The best bet would be to take any train to Bristol Parkway and change there for GWR through to London.

As others have said, it wouldn't normally be valid via Birmingham. You can go via Bristol Group (and optionally also Bath and Chippenham) though.

Thanks all for the helpful replies.
I’ve now changed my travel date to Saturday although I’m now concerned about the possibility of over running engineering works at Paddington.
Changing the hotel booking was easy but I made the mistake of booking the train on the CrossCountry app. I assumed a ticket booked in advance was an “advance ticket “. The app informed me I couldn’t change the booking so had to make a new booking then cancel the original which I did. So now not only do I have to pay £10 to cancel but also get the tickets from the machine at the station and post them to CrossCountry for them to “consider a refund “