Hi Gill,
If pressing the fuse makes it work then it's a problem with the fuse/box. If the fuse when pressed is moving sideways and working it would suggest a loose fuse holder, the hole where the fuse fits is metal lined to be a socket or all is moving and the wire/s at the back of the socket are loose.
Try another fuse.
Try a fuse that you have twisted the two blades slightly so the fuse is a tighter fit.
Try a thin screwdriver and with everything switched off or the battery disconnected fiddle with the sides of the socket to move the metal lining towards the middle so it grips the fuse tighter.
Unscrew fuse box and see if the wiring at the rear is loose or that particular socket has a problem others don't have.
Charring around the socket may be a sign of a loose fitting.
If the socket is damaged/burnt or? Is their a spare fuse place that is not in use if so swap wires to that one and see how you go.
If none of the above find someone who knows more than you to have a look, I do appreciate that is why you have posted this problem!
Hope you get sorted
Boots