Oh, I dunno about lying, but we have been known to view things with rose-tinted specs a lot, or only one side of the story. Just ask Tribesman.

We tend to just skip over bits of history where we were...not very nice people...such as Cromwells jaunt to Ireland, or the Concentration camps during the Second Boer War.
It's the old adage that nearly always rings true, history is written by the victors.

It's a case of walking that fine line between being proud of your nation and being patriotic to the point of jingoism. I admit, I sometimes stray across that line, particularly when it comes to harking back to the days of the Empire, but I try to keep myself grounded by reminding myself of things like the Jallianwala Bagh massacre, but even then it's hard, as someone born in England, and aware of the days of Empire, not to feel a little bit of nationalistic pride in our accomplishments of the era, even if they were written in the blood of many others. Of course, the milage may vary, I think most people in this country of my age are only aware of what is on television or facebook, and couldn't really give two hoots about history outside Downton Abbey perhaps. A mixed blessing, because it lowers the likelihood of nationalistic tendencies amongst the populace of the future (as the BNP are finding out, although the fact that they are morons also works against them) but it also builds walls around us and fractures society a bit when you don't look at where you've come from before you look at where you're going.
Still, c'est la vie et c'est la guerre, as my terrible GCSE French would say.