Thank you Valda for responding to my query so quickly.
I tried to follow up the lead I was given here about Joseph and Charlotte Mawbey, about her burial at Christ Church, Southwark in 1810. This sounded promising, but it seems I cannot look at these records online. I would like to know her surname.
The census material sounds too late.
A George Mabey, a servant from Surrey, was transported to NSW in around 1826 and this may have been my ancestor.
George Mawbey's death certificate suggests he arrived in 1832, but information for this was provided by his 17 year old daughter. I'm wondering if he spent time in a workhouse. His letter published in the Australian newspaper, and the fact he later worked as a schoolmaster at a small Church of England diocesan school, indicate he was well educated.
It appears he was also involved in professional theatre, so his spoken English must have been good too.
I don't think his father Joseph came to Australia with him now.