i have terrible terrible ulcers - i get a proper infection where they all crowd round the entrance to my throat and i cant swallow anything without proper pain. they're all huge too and last for weeks and weeks - they're evil. my doctor prescribes me corsodyl for them - you can buy it at the chemist. make sure you buy the menthol variety as the original is so disgusting it made me sick the first time that i accidentally swallowed it. you can gargle with it or swill it around your mouth and although it tastes foul, it really does speed up the ulcer disappearance. you can also get some stuff called medigel - comes in a tube and properly numbs them. its great.
hope that helps.