Hi Steve
Yes i have i worked a few blokes who told me the sleepers, mail trains ran that way after the Bridgend derailment so it's very highly likely there were Westerns somewhere.
Also what about a Hymek over Crumlin viaduct,1963 a mate of mine who was a Signalman on the VON told me towards the end a Hymek with a Inspection saloon came up from the
Neath direction no photo sorry.
D1054 Western Governer took the Royal train to Merthyr with Queen after the Aberfan incident 1966.
I have photo somewhere of a Hymek on a breakdown train at Ystrad Mymach in 1967.