Keith, this is definitely the right track, and I agree with what Sue says. I was wrong in my supposition that the 1953 letters of administration related to your great-grandfather Charles (husband of MEAF). In fact they must relate to his father Charles (husband of MJG).
Now that I have your e-mail address I will write to you. I should be able to help you with the earlier generations and later Manx families, and we should be able to help each other with the later generations in England. I might not be able to let you have much detail this side of Christmas, though.
Philip Allen