On a transcript of the Wedmore parish records I found an entry under baptisms for Elizabetha Bunn for 18 Jul 1703, the father is Gulielmi Bunn and the mother is Elizabethae Bunn. There is also a son, Gulielmus, baptised on 22 Apr 1705.
On the same transcript Guilielmus Bunn married Elizabetham Andrews on 7 Apr 1702.
Looks like a match to me and a possible alternative spelling of William!
Hope this is of some use to you.
Rob