I have a Marshall MG30FDX guitar amp that has a suspect headphone socket and
believe me, for the sanity of my wife and our neighbours, I _need_ the
headphone socket to work! :-)

I'm not into electronics at all and don't have the necessary equipment to
de-solder the existing socket from the pcb and install a new one, but
luckily a friend of mine does, so he's going to do it for me. As I live
within walking distance of CPC, I was just going to get one from there but
it's not the sort of place where you can go in and ask advice easily. It's
more like Argos and Screwfix where you pick stuff from a catalogue first
then go to the counter with catalogue numbers, so when I searched the
website and it came back with more than a dozen results, I'm lost.

I've opened the case and it physically looks like this one, but switched?
unswitched? I'm assuming switched because as you plug in the headphones, it
cuts out the speaker but I'd be happier if someone could confirm it.
http://cpc.farnell.com/neutrik/nmj6h...ose/dp/AV11183

The schematic for the amp, if you need it, is here
http://www.amparchives.com/Amp%20Arc...%20MG30DFX.pdf

or http://tinyurl.com/46enmwj if the above doesn't work.

TIA