Sorry for the delay in replying.
My great grandmother was Mary Ann Smoothy. She was born at Ickleton, Cambridgeshire. As I am sure you know, your ancestors were from Hadstock which is very near Ickleton but across the county boundary in Essex. I have found very obscure connections but not one bringing your line and mine together. The name is unusual and they are from the same area so I am confident that if I could get past the brick walls I have hit with both lines, I would find it.
With your line I get to the middle of the 18th century and the marriage of Albert Smoothy to Hannah Buck (Saffron Walden, Essex 20 Dec 1749). They had 7 children. I think they were probably all born in Suffolk but I cannot be certain because none of them were baptised as children.
With my line the earliest Smoothy I have is John who married Sarah Farrands at Barnardiston, Suffolk on 28 Aug 1712. I don't know where he was born.
Apart from the name Smoothy there is one other small clue suggesting a connection. Hannah and Albert's oldest son, James, married Mary Kemball at Dalham, Suffolk on 1 Jan 1781. Kemball crops up as a forename in the family after that date. Curiously, a couple of my lot also have the forename Kemball. The first of them was Job Kemball Smoothy who emigrated to Maryborough, Queensland with his parents (George Smoothy and Martha Hayden)and siblings in 1874.
Are you in touch with Diane Mathews (nee Smoothy)? You definitely have a connection. Di and I have helped each other with Smoothy research for several years although neither of us has done much in the last 2 or 3 years.
I have opened my Ancestry Tree for you. It is way out of date but I can probably plug some gaps and provide sources if you do not mind using e-mail. My address is firstname.lastname@example.org