I think part of the problem with GW replacement stock was the length of bay platforms 6 and 10 at Reading and to some extent the low level of demand at the intermediate stations. 117s continued for a whole 10 years after the 210s came on the scene.I'd argue it was more of a shame they didn't get the wires up (if only to Reading) and got 317s or similar instead.
Wires were clearly years away if they couldn't even justify replacement stock.