SAFETY. You can read in various threads here that there are safety issues when working on valve radios. But in addition there is a particular point to watch with regard to your set.
There will be voltages on the mains tapping connections on top of the mains transformer. If the plug has been wired so that the on/off switch is in the live conductor there will be about 40 volts (with respect to earth) on the 200-215 volt tapping when the set is switched on. You can feel 40 volts but it is relatively harmless. If the plug is wired so that the on/off switch is in the neutral conductor there will be full mains voltage on the 240 - 255 volt tapping. This voltage will be present when the set is plugged in
regardless of whether or not the set is switched off. THIS PRESENTS A SIGNIFICANT DANGER.
Be aware of this as it is easy to put your hand somewhere silly if you are distracted. Ideally you should make up an insulated cover for the top of the transformer so you cannot touch the tappings.