Igor, (am I correct?)
I'll answer in English. Thanks for your hunta/djunta remarks. Most interesting! I agree, I think the words are of foreign derivation - probably latin-american.
As to your questions, pronounciation in English is somewhat unpredictable. the vowel sound in THIS is short, similar in a way to ы and the 's' in unvoiced, unlike IS where it sounds like a soft Z. THESE rhymes with CHEESE or even PLEASE.
Oh yes, there is a great difference between English and British! England alone refers to the land of England and excludes Wales, Scotland and Northern Ireland. British covers all of these including England. Cornwall is a county (графство), or more accurately a duchy (from 'duke' герцог - герцогство) and the Cornish have their own celtic language and a separatist movement. We Cornish do not think of ourselves as English! England is really a Norman invention and after nearly 1000 years the arguments continue! Всего хорошего, Майк