Thanks everyone for the advice so far, this has all proved very useful. I have checked the census records as suggested and they all seem to fit very well with the information I already have.
This led me to discovering that Henry's mother Sarah did indeed marry Richard Reeves.
Trunkybun1 I have some information on Sarah's father and grandfather for you.
Father: George Moon baptised 05.02.1786 Brookland and married Elizabeth Shrewsbury 10.07.1815 New Romney no death information as yet.
Grandfather: Thomas Moon no baptism record, married Jane Maybourne 10.04.1784 Romney Marsh no death information as yet.
Other information about Sarah's brothers and sisters I got from
http://freereg.rootsweb.com/and searched the parish records for Moon baptisms.
Thank you bearkat for the links - I knew about the Mid Kent Marriages website, but the Romney Marsh baptisms will come in very useful.
If anyone has any idea what happened to Henry Moon I would be most grateful, I am really stuck as to where to look as every death record for a Henry Moon doesn't seem to match the age he would have been from his baptism record?
Thanks everyone