"I couldn't get over his Britishness"
"I dated her because of her Britishness"
"My family is full of Britishness"
"I have more Britishness in my body than anybody else"
When the overall country (Britain) is used to spread the dissapointment or a failure of an individual region (Scotland/Ireland/Wales/but normally England). When regions pick and choose their Britishness to suit them.
When Henman loses a tennis match, it's a sad day for "Britain", not "England", and when Murray wins a match, it's a good day for "Britain" not "Scotland". Perhaps I'm biased (being a scot) but it always seems that way. Selective Britishness! Hah!