Well we have oboth got older since you posted your message, but I have only just seen it!!!
Not sure if this info is any good to you, but being a Gritton myself, would like to share it with you.
I have a branch I call the 'Shoreditch Gritton's' - They originate from Joseph Gritton, born abt 1763 in Dorchester Dorset. He has a sister, Elizabeth who marries William Ballard in 1797 in the City of London.Elizabeth's daughter Mary Ann Ballard, married Joseph's son, John Gritton (it's the only 1st cousin marriage I have found in the whole tree).Joseph Gritton Snr, was employed at the Bank of England together with 3 of his sons.I have been to the archive there and traced them all.The extended family prove to be a very interesting bunch of people.
As I say, not sure if this is any good to you.I have nothing futher back than Joseph as yet.