The braking light was easy, the bulb was the bad part. I checked it once, seemed fine, but when I switched the left and right bulb it became obvious that it was the bulb. I (hopefully) mended my exhaust properly with some gumgum exhaust paste.
Had a go at the brakes today and yesterday with my dad.
The left brake does function a little, but it's so little that you can still move the weel (car jacked up) with your hand when your applying the brakes.
We took both the right and rear brake partly apart (the fluid passes through the right one first) as far as that we took out the brake pads to compare them. The pads on the right brake are worn down quite a lot more then the left ones; the left brake hasn't functioned in quite some time! We sprayed all the moving parts (obviously not the disc) with some brake cleaner and gave it a proper clean. We inspected all the braking lines, hoses, connectors, cables etc etc etc and they all seemed in good nick, quite a lot of them looked brand spanking new actually!
After this we put the brakes back together (quite a fiddly job, but once you know how it works it's a piece of cake) and had another go. No difference... After that we decided it might be a good idea to bleed the system, we discovered that there was no air at all in the braking system. Besides that, all the fluid levels are ok and I can't imagine the system has a leak! (which would mean that the fluid levels would be low by now).
Anyone got any clues?