JOHNSON of Guernsey

[glenysjr]

Hello:  I have an original parish entry (in French) from St. Martin's Parish, Guernsey for the baptism of William, son of Thomas JOHNSON and of Lettice JOHNSON (Royal Artillery), born October 12th, 1812 and baptised 25th following.  Godfathers:  William ASHEM and Jean BELL.  Godmother, Elizabeth ASHMEN.

Would it be possible to a) see if there are any more children to Thomas and Letitia JOHNSON between 1808 and 1820 at St. Martin's; and b) explain to me if the godparents would be relatives or friends. (I am thinking that William ASHEM and Elizabeth ASHMEN could be husband and wife, with a spelling error in their surnames). 

William JOHNSON went on to marry Mary Ann LEWIN at St. Mary Lambeth, Surrey, England in 1834 and died in Camberwell, Surrey in 1857.  She was from Camberwell.

Thank you for any help.
Glenys