Railway Gazette has published a comprehensive update on the 80x (and 385) situation.
It appears that a medium/long-term repair programme is envisaged for the entire fleets (80x and 385) which is likely to take until the end of 2022.
The programme will need specialist people and equipment, and a location for the work has still to be found.
Two 80x (800 026 and 802 205) are to be guinea pigs for establishing the best repair policy, which is still not defined.
For contingency, GWR is looking at using ex-EMR HST sets with their own power cars (for ATP), more 387s and a 67/Mk2 rake.
The DfT is said to be keen for TPE to activate Mk5 rakes so that 3x802 can be loaned to GWR (without ATP).
Class 80x recovery plan takes shape | Rail Business UK | Railway Gazette International