chubbytaxman on Family Tree Circles

Hi, my name is Ray and I have been doing genealogy on and off for a few years now. Mostly "off" as I have found a brick wall. I am hoping that someone will supply me a hammer to knock it down. Not having any subscriptions to overseas archives is a hinderance, but, I am confident of having one within the next year or so.
My "brick wall" is with a certain convict - yes I can say I have one as well as heaps of others. He originally hailed from a place he referred to as "Boxford, England" on his conviction papers that were lodged at Somerset Assizes Court circa 1820.
He was listed as 27 years old so that would put him born about 1793 at this "Boxford" place. I can track him from his arrival here in Australia (Tasmania to be exact), pardon granted and subsequent relocation to New Zealand. He married a lady called Ann (Harriet) Miskellion? and had about 13 children. All of these took up residence in NZ and had subsequent families of their own. A few migrated back to Australia - where one was my dad. My problems lie mainly prior to his conviction in good ole England. He simply does not show up on anything I can search.
Any help / pointers are greatly appreciated.
Thank you for looking
Ray Smoothy