English or British?

Yesterday at work I was feeling particularly uninspired. Normally I'm pretty constantly and chug on pretty well but yesterday for no particular reason (though later I realised it was perhaps due to having a restless night previously), I had no energy to keep working by midday...which is when I got a call that normally I'd let wash over me as a loony but decided to argue the point just to relieve the tedium (I literally went up to one of our officers and said "Jacqui, I've got a problem...", "What's that?", "I can't be arsed...")

Anyway a woman (maybe in her 40s, hard to tell over the phone) called in to clarify a point in some documentation then said she wanted to make a complaint. I said OK then she went on to explain how she (and plenty of others) found it offensive that when asked for her ethnicity, she was given the options of White British, White Irish or White Other. When I explained that she needs to select White British, she went into a rage and proclaimed "But I'm not British, I'm English!". When I said that is covered under White British, she denied the fact and still claimed she was English and not British. From that point, the conversation went a bit like this:

"Yes, but England is part of Britain..."
"GREAT Britain!"
"Yes, GREAT Britain, so that makes you British."
"No, I'm ENGLISH! I was born and raised in ENGLAND!"
"...which is part of Britain..."
"Listen, if you told a Scottish person they were British, they'd be very offended! They're Scottish!!"

Nice of her to speak for all Scots and I'm sure if you called a Scot English (or Welsh), they would be offended. I'm not convinced they'd be offended by being called British, although I'm sure there's a few Scots who would like to gain independence from the UK...

Anyway, the debate raged until she said:

"I am from England, NOT Britain!"
"Well as England is PART of Britain, under that logic if you come from London, you can't claim to be English..."

And this is the part where I just gave up arguing....

"Now you're just splitting hairs!"

Pot, meet black kettle...

So, what ethnicity would you classify yourself as?