Why hasn't mustard been suggested yet
mustn't burst into flames during use
Get yourself a "Zip-it" drain cleaner tool. They work great.
They sell caustic soda in boots, might be closer than b&q for you.
Can't you use a knife to cut the hair trapped around the trap? Should fall out nicely then if you've taken the whole thing apart.
Have you done it yet??
video+youtube or it didn't happen
Sounds like the only thing that could be more disgusting than sebacious cysts being burst