I also saw your entry on the 'Scotland'Forum,and I reckon this is your man:
CENSUS 1851:County of Ayrshire,Parish of Dalry.
At 15 Kerrsland Row,Garnock:
-Thomas Wilson,head,mar,60,Pauper(former Ironstone Miner),b.Ireland
-William,son,unm,20,Teacher of Mormonism,and Ironstone Miner,b.Ireland
As Joseph was a particulary rare name for a boy in the Highlands of Scotland,I would assume his birthplace of Ireland is correct.His father,or grandfather may have been Scottish,however.
Garnock is located about 10 miles north-west of Saltcoats(the middle"t"is silent).