My battery light in my TR has been playing up for a while (flicking on and off), and tonight while i was driving home from school the dash lights that light up my speedo and other instraments started diming a bit and brightening back up.
So i guess this would be my alternator? as the battery still looks like its in new nick.

check the terminals on the battery and mke sure they're on tight. Also if it's a cheap battery check the voltage across it as I had a cheap one in my car when I brought it and I had a similar prob on short runs and when I checked the voltage it was only 10 or 11 volts.

The alternator is faulty. Sounds like worn brushes to me. You can either replace the brushes or buy a new/reco alternator. Best way to test is to push on the alternator plug while the engine is running, making sure the light is on. You will hear the engine change tone and the light should turn off. this will indicate worn brushes. Good luck!

Check the regulator, I had similar problem on a TP, I changed it no more trouble