Pug 306 1998 - Radio stopped working

In our 1998 Peugeot 306 the original radio seems to be playing up.

This morning I turned on the ignition and the radio display came on
(showing the RDS info of the channel it was tuned to) - however no audio
came out. I tried turning the audio up using the stalk control and
nothing happened - tried the controls on the radio - nothing either.

I then pressed the power button and it turned the radio/display off.
Attempting to turn it back on again did nothing (the display doesn't
come on). When turning the ignition off, the security LED on the radio
starts flashing (as normal).

The weather has been quite hot recently (last few days/week) but up
until now it's been working fine. The only thing I've noticed in the
last month or so is that sometimes, when using the stalk to adjust the
volume, it seems to stick and the volume keeps going down to 0. A
waggle of the stick and it works again. I've tried waggling the stick
this time and still the radio seems to refuse to turn on.

Any ideas? I doubt it's a fuse problem (as the display worked fine
until I turned it off, yet the controls didn't - so power was getting to
the radio whilst it was having a problem). Should I try disconnecting
the power and see what happens? I should have the radio code - the
dealer looked it up and wrote it on a card when I pointed out to them
that they failed to provide it when we bought the card (2nd hand).
However, that was in 2001 or so, and I've never yet had need to use this
code - so until I know it works, I'm a little loathed to disconnect the
radio - just in case they didn't get the right details!

Thanks

D