not up one's own ***

I've recently read a sentence (slang, without a doubt) that I don't understand:

"They're from Coventry, mate. They're working lads, they're normal boys. They've gone to all the schools we've gone to. They're not up their own ***." 

(NME, 19 April 2008, p. 22) 

What does "being up one's own ***" mean ? 

P.S.: Apparently there's a word that is automatically censored. It starts with A, continues with R, S, and ends with E.... 

To be stuck up is to act superior to others, to look down on others, to exaggerate one's own importance, to put on airs. 

CJ 

full of a sense of their own importance/arrogant/think how wonderful they are.