Hi Adrian and Ruskie
Not sure if there may be two William Cloys running around both born at the same time in Wigtownshire

There is an online tree I think, Ruskie, for the William Cloy/Niblock (whose birth shows as submitted on IGI) who looks to have married a Catherine McGinn in 1856. His parents are given as William and Jean (Niblock) on that IGI entry (likely birth illegitimate?). His years are 1828-1907, death in Dalry, Ayrshire.
This is their entry in 1861:
William Niblock 32, coal mine lab., b. Old Luce, Wigtownshire
Catherine Niblock 26
Mary Niblock 9
Jean Niblock 7
Bryce Niblock 3
Address: Main Road-n Side, St Quivox and Newton on Ayr, Ayrshire
Monica