You're wrong... there is no Welsh equivalent of the "Queen's English" or Received Pronunciation. In English, anything pronounced differently to the Standard pronunciation is technically incorrect and is considered "dialect" whereas in Welsh, as there is no "standard" all regional variations of pronunciation are equally valid. Of course, certain North Walians will tell you different and that anything other than North Walian Welsh is not "correct Welsh",
Spot on. North Walians have a bit of a case for the claim, given the fact that the earliest Welsh dictionaries were written by Northeners, but there's no primacy for any form of colloquial, regional Welsh. There
is a standard form of literary Welsh, but that's the written form you find in books, which is old fashioned by the standards of everyday conversation. If you use literary Welsh on the street with people, they'll wonder why you're "talking like a book"...
There is also a lot of nonsense spoken about Welsh being a phonetic language.. certainly in everyday spoken Welsh it isn't... take "how are you" in Welsh: sut ydych chi... phoneticly it would be said "SEET uh-dikh khee" but it isn't it's said "Should a key"!
Ah, here you seem to be confusing phonicity(sp?) with dialectualism. The language is phonetic, in that only one* sound is represented by each letter/digraph, and it doesn't change from word to word. (*Vowels have short and long forms, depending on whether they're in a stressed syllable, but that's still very consistent.) There's nothing like the situation with 'c' in English, which can represent two different sounds (car, circle) but without much guidance which is usen where.
The pronunciation of vowels will change from place to place within Wales, for example as an Anglesey lad I tend to pronounce several vowels (such as 'e') more like an 'a' than other areas. (Consonants are quite constant.) This is the influence of accent. The radically different pronunciation for "syt ydych chi" that you describe is dialect.
The first word's change is largely a regional variation through accent, and if one were to write in that dialect it would be done "shwt". (Note it's a change of vowel sound, along with a blur of 's' into 'sh' next to a vowel.)
The second word has changed due to skipping out part of the word "ydych". Rather than use the full formal form, most dialects use a reduced, one-syllable form of this common, everyday word. In my neck of the world, we tend to drop the first letter, giving 'dych. (In an Anglesey accent, the vowel also turns into an 'a' sound, as I described above.) Other areas drop the first two letters (giving 'ych), and in West Wales the accent comes into play, turning the long 'y' sound into a long 'i' (ee), or variations thereof (ay, ey) depending on where you are.
On the other hand, if one were reading the more formal phrase "syt ydych chi" from a book or sign, one would usually just read it out as is, with accent on the vowels, but without reprocessing the words dialectually.
Note that these issues of dialect don't tend to be an issue with Welsh placenames in Wales: the names of places are considered formal, so you'll only find variations in vowels due to accent. (Blaenau sounds like "Blaena" Ffestiniog up north. or "Blaine" Gwent down south). There are local dialectual nicknames (such as 'Stiniog for the above) but these exist in parallel to the formal names, not as a replacement.