What records are available for HULL area ca 1725?

I'm currently stone-walled on my ancestor, William ASHBY, b. St. Mary's parish, HULL, ca 1725.
William served in the 27th Regiment of Foot from ca 1744 to 1767, but other than a copy of his military discharge papers which indicated he was born in St. Mary's parish, HULL, in 1725, I know very little.

I've checked the christianings records for St. Mary's for this period and come up empty; Liz suggested that there were some records of ASHBYs in the Holy Trinity parish in the 173x time frame.

I expect to have a few days in Salt Lake City in September and plan to spend time at the Family History LIbrary. I will look up the Holy Trinity records while there.

I'm looking for suggestions on what records may be available for the HULL area in the 1730's.

Thanks

wes