what does it mean to be british?

It means having an amazing ability to 'keep going' no matter what
calamity comes our way.

However, the recent loss of the Rugby Union match with France and the
loss of the 2nd Cricket Test with India are now severely testing us.

Some of us are even thinking of resigning.

Disillusioned of Hove

Jinko nationalist, tempered with humour and such a sense of native
superiority that one can with nonchalance bear the kind of setbacks
Probono mentions.

Not a lot.  There is no "British" identity.  The island of Great
Britain contains the English, Scottish, Welsh, and Cornish peoples
(sorry if I've missed any).  Many people equate British and English,
which is not entirely correct,

It means ths Scots, the Welsh, the Irish and the English hate you.

Oh dear, Horatio, you missed the most important people of the lot: the Irish.

(My mother's father hailed from the Emerald Isle.)

Ah, well, that explains a lot ... :)

I didn't count the Irish, as they have tehir own Island.  Granted it's
in the "British Isles", but they don't share an Island with England. 
(Although the U.K. does occupy Ulster, I'll admit.)

Begorrah, Horatio, Are you saying that we've been a-fighting each
other for all these years for NOTHING?

Bryan, 

Wars, etc. are usually useless nuisance. 

Couldn't your line be written also regarding Palestine, Chechniya,
Yugoslavia, Iraq, etc.?

I totally agree, Polly, and there were many others: Korea, Vietnam, Argentina ...

Not forgetting the punch-ups scheduled for the Football World Cup in
your neck of the woods.

Me? I'll be wearing a suit of armour ...

Just in case.