If the name, age and area are all wrong - then on the face of it, it doesn't look a very good bet!
When you say the one you found (wrong name, wrong age and wrong area!!) has a surname which appears in the family, are we talking an unusual name (e.g Clutterbuck-Winstanley) or a more frequently found name (Taylor, Watson, Henderson, for example) ?
What else is known about the grandad? his marriage, children etc? Sometimes if you build up a picture of a person from many angles it helps - you may find for example that he did actually have a differetn surnmae. Or you may find that there is no hint of a different surname, in which case why would one appear at this death.