Thanks. I've always used a "+" sign to mark the cathode, like they do on bridge rectifiers. It wasn't until I sent a board off to China for assembly that I realised that I'd not been consistent, and my LEDs were labelled with a "+" sign for their positive terminals.
I think I'll go for A and K. There isn't always room by the side to draw a diode symbol, and I don't like pcb idents that are covered up by the component.