William Slatter, blacksmith, took an apprentice in 1745 as did Nicholas Slatter, blacksmith, in 1805. so presumably William that is married to Mercy. The other William married Martha in 1748.
John Hayward, given 60 years, is in the Union as an agricultural labourer in 1841, so not much hope of a Will there! He married Jemima Selmes in 1803.
There is a marriage of a John Slatter in 1797 at Greenwich in an index but I cannot see the wife's name as yet. Greenwich Chapel seems to have connections to Battle.