Aside, I wonder how long UK dialects will survive: my kids often come out with US Americanisms - of both word choice [garbage] and pronounciation - because of the media they consume.
I do not know much about UK dialects, but someday US will speak a Kiwi-influenced dialect. Received Pronunciation will survive due to preservation efforts.
My point is that different people pronounce things as they are used to, reflecting it in a writing system leads to complexity and inconsistency.