Offensiveness of British Swear Words

Howdy folks!

I’ve written a short science fiction story, set in contemporary London.  I’m in the process of submitting it to magazines and websites that publish short sci-fi, but there’s something that’s puzzling me.  A fair few of the publications ask that the content of the piece be suitable for a PG-13 audience, in particular in regards to the level of obscene language used.  I’m English, but most of the appropriate magazines are based in the States.  I’ve used a few English colloquialisms in the dialogue in my story, but I’m not sure how offensive these would be to an American reader.  Also, I don’t really know what a PG-13 rating means in regard to the level of bad language.  For example, there are plenty of swear words in the movie Super 8, which is rated PG-13.  I know that a PG-13 movie can contain a single, non-sexual f-bomb, but I can't find any information about the other swear words that can be used, or the number that is permissible.     

So, would any of the following words be offensive to an American reader:

Wanker

Tosser

Twat

Bollocks

Arse

Piss

Prick

Bloody

Git

Sod

Bugger

Shite

Cock-up

There is only one instance of the S-word in my story.  

There's no violent or sexual content in the story, but lots of drinking and cigarette smoking, and some gross-out stuff.  

Terms searched:  PG-13 swearing,  British swear words America offensive, how many swear words in a PG-13.

Thanks in advance for your help!