Mr Moose,
The speaker is definitely not original as it is indeed mounted on a piece of the donor sets front panel, they even used to cannibalise stuff back then! The speaker that is there is absolutely shot mechanically, totally seized up & cone in pieces. As it's a dynamic type I'll keep the coil in circuit.
MerlinMaxwell,
McMurdo,
From what I can find out Philco imported sets to the UK for the UK market, as you say. Apparently even in the USA these sets are rare. I thought the chassis was a bit "run of the mill" myself! The fact it fits exactly & there are no extra holes even underneath leads me to think it (or something darn close) is original.
I've noticed that just about every panel or piece of wood that can be removed has the number 783 either in chalk or stamped. Perhaps a serial number?
I'll be having a much deeper look at the weekend, best get on with some work I suppose!