Thanks for your comments Marcc
There were 2 service tags still attached to the radio chassis, one was for a repair in October 1952
fault described as "volume weak" and the other in May 1963 fault "stopped".
I guess the mods were made during these repairs and the 6F6G being replaced with 6V6GT.
Will replace both filter caps with original value of 8μF. The 32μF cap is leaking electrolyte.
Haven't checked anything else as yet.

Deleted comment as accidentally posted twice.

Stopped! Fairly broad spectrum, starting at the GPO.

Those caramel Polyesters are normally OK but I have seen the odd one split the jacket at the end. Often coils go open on a corrosive joint, in such cases one can sometimes be lucky & fix it. Some rosins were corrosive; However it was always recommended to remove it (Circuit board cleaner) and coat the joint ( Circuit board lacquer) to reduce electrolytic corrosion.

6V6 and 6F6 are different; 6V6 is more power hungry & has a grid bias of -12.6, -16.5 for 6F6: That can have a significant affect on the bias.

It's got 6F6 stenciled on the chassis under the second valve socket from the right in the chassis top photo shown?

You can generally put a 6V6 in a socket intended for a 6F6 and all will be well. The higher bias will be compensated for by the higher plate load of 7k vs 5k, Distortion will be marginally higher, I doubt you'd hear the difference though.

A 6F6 is going to be harder to get, 6V6 not so.