A slight aside from the "thee" in discussion - a word I heard a few years ago here in Yorkshire from a young woman of about 30 - "I've forgotten to put my middings out!" This obviously is a direct descent from "midden" as she was referring to her dustbin. She comes originally from Kippax, between Castleford and Leeds, just to the West of a Roman Road, and an old settlement, by its name.

I am an East Midlander by birth, me ducks, but I have moved round the country during my life. If you read the "Hey Up Me Duck" dialect books by the late Rick Scollins on the South/Derbyshire dialect (Derby, Ilkeston, Heanor, Ripley,&c), you will find "thee/tha" in use there. I have used "siling down" for many years, but not so much of late. I first remember using it when I lived in North Derbyshire (Whaley Bridge) between the ages of 6 and 14, as I daresay much of my language was formed in those years. (We moved up there from a year in Dorset, where I started school, so what that's influenced I don't know!) We moved back to South Derbyshire from North Derbyshire, and all I used to get was, "Doesn't she talk like 'Coronation Street'!"
I think it was mainly Celtic tribes in the north, and Saxon/Danish in the south, if my memory serves me right.

A little extra. When I first went to Grammar School, my English teacher was a graduate in Anglo-Saxon. She told us that the "y" in "ye" as it is written in "Olde English" is taken from the Anglo-Saxon letter pronounced "thorn", which looks a bit like a "y", but more closed at the top. This letter is pronounced "th", which gives us "the" from "ye". Interestingly, "the" is usually lenghthened to "thee" in front of a word beginning with a vowel.

I don't want to make this creep off into a pronunciation debate, so I'm going now.

Andrea