Hi Sarah
I can certainly help with dates etc from the Parish registers and am building quite a large descendancy sheet for your George from Great Tew/Maidenhead so if you'd like to contact me on
carol@alansmith.co.uk I can email it to you.
There's a very eerie coincidence here - he lived at 59 Garden Cottages in Maidenhead. My Gibbard connection is through my mother's father - his mother married twice, the second time to a Gibbard who may or not be connected to your Great Tew ancestors. My mother's mother was a Pearce and her elder brother lived in Garden Cottages in the early 1900's - not sure which one - but his name was also George! Garden Cottages was a row of three very long terrace blocks, the front row of which faced the allottments - hence Garden Cottages, I presume. They have long since been knocked down and the whole area has been redeveloped.
Kind regards
Carol