I don't know how polls are conducted over in Scotland but around here they are either annoying (like telemarketing calls), sometimes worded to encourage an outcome "Dihydrogen monoxide is the top ingredient in your tap water. Would you drink your tap water?"

Even if the questions are straight forward, folk usually are reluctant to share their political standings or religious views with strangers. I think some polls might use non-direct questions as indicators to what direction you had voted, again, may not indicate how they vote.