My mum was half Manc and half Devonian (to one gen) and my dad is half Irish and half North Hants to one gen. I can easily claim all UK nationalities within two generations and German within four. Cornwall, 14th gen via mum, Padstow. I've got the lot!
In reality, you end up with a tea pot going cold with stewed tea in it and you wack some milk and tea in a cup.
Get a grip and drink tea and stop pontificating about the stuff. Its just tea. Yummy!