When I used to teach English as a foreign language, the foreign students would absolutely light up when swear words came up in conversation. Knowing what colorful language is used by locals is fun, whether you speak the mother tongue or not. The British selection of swear words is far superior to the American (not unlike the cheese). After years of living here, I've not only learned new swear words but I have also learned that some American profanity isn't considered as offensive here and vice versa. Here are a few noteworthy expressions/differences:
cock up - A uniquely British expression which describes errors of epic proportions. It can be used as a verb: "My driving test was a nightmare, I cocked the whole thing up!" or as a noun, "I got lost and was over an hour late; what a total cock up!"
bitch - Yes, it is used in the same manner here as we use it in America. i.e. "I can't believe how rude she was, what a bitch!" But here they still use it when talking about female dogs. I asked an elderly woman at the bus stop (while she was petting Abby) if she herself owned any dogs and this sweet old lady replied, "Oh yes, I've got a dog and 2 bitches".
fanny - This one makes Brits giggle. You see, to Americans it's just a cute nickname for a bum. But for Brits, fanny is a very specific word for a vagina. Imagine their shock and laughter at hearing us say, "I've eaten so much my fanny has just tripled in size; hope it doesn't break the chair..." or "I won't bother taking my purse tonight, my fanny pack is just fine."
on my tits - You probably shouldn't say this one in a job interview or anywhere else where you're trying to make a good impression but it is used in every day language and thus isn't really profanity. It means when something really gets on your nerves. "The way he always interrupts her when she's talking, it really gets on my tits."
pissed - In Britain this word on its own simply means drunk, it does not mean angry as it does in America."Man, I had no idea you were such a lightweight, only 2 beers you were totally pissed!" As an American, I have had to train myself on this one because the difference can create huge issues. Example: "Last night on the way home on the motorway this guy cut me off and I was so pissed!"...this means to me (as an American) that I was angry but to a Brit that I was drunk driving!