>>The pronunciation of "do" is to my ear somewhere between "day" and "dee", almost but not quite an exact rhyme for "me". I think it's sometimes represented by the spelling "dae".

I grew up in Geordieland and can confidently say that the pronunciation is a straight ahead "dee" in the Newcastle area - it doesn't really tend toward "dae/day" until you get a little further south into Sunderland and Durham territory. There's actually a lot of variation in Geordie pronunciations though, even in the same area. Take the pronunciation of the word "eight" in Geordie. It's a toss up whether someone says "ite" or "eight" with a Geordie "a" for the "ei." Personally I use both depending on whim.

Same with "thowt" really. Even among the old timers, "thowt" and "thought" are both used interchangably.