Jackie, there are 21 William or Wm Cain/Cane/Caine in the 1841 census that I have found, whose age given there is within 2 years of 1826. No relationships are given, nor parish of birth, and adult ages are rounded, so, as you wrote, he won't be easy to identify. Were there any relatives living with him in a later census? Have you checked his marriage record to see whether further information was given (e.g. father's name and occupation)? Some parishes showed extra information earlier than others.
What was his later occupation?

Brian Lawson's wills index is at www.iomfhs.im/lawsons/LawsonBMD/wills/c-will.html or at: lawsonsiom.freevar.com/ (see Main Wills Index here, as well as Recent transcripts). You need to read the guide to these.

Sue