One thing to watch is that some of these sets actually had the dropper incorporated in the line cord (nichrome resistance wire protected by an asbestos coating). The 1940s saw some American "midget" sets imported into Britain, and to drop our 200 to 250V supply down the line cord was often 9 ft. long! The problems arose if somebody decided to shorten the cord.
Sven mentioned replacing the capacitors. Just one thing to watch closely is the voltage ratings. In some points in the circuit a quite high rating is needed -- Any top-cut capacitor across the audio output transformer primary for example. The voltage swing when driven loud meant that manufacturers often needed 500 or even 750V types in that position, even though the HT (B+) line is of much more moderate voltage.
