If memory serves, every member has a right to view the books of accounts of the company, which includes what unit are paid up and who is in arrears. I think every member may also view the register of members. There are a couple of threads on that topic around here.
Not sure if Data Protection Act applies.
The first year in my development, they decided to be up front, agent and his helpers checked everyone in at the door, agent checked the ledger and issued a yellow "vote" card. If there was agro the agent dealt with it, told them to read the articles and memo of association, and asked them why they had not paid their fees, when they would be paying their fees, if they'd like to pay now they can vote, etc....? Explained that they could come in, but would not be able to vote, etc.
They arranged the room so there was a bot of a hall/alcove for the check in conversation, to try to preserve some politeness!
Be prepared for plenty of shouting and screaming though, from what i've seen the non paying members tend to be most vocal.
Remember, they're the ones at fault, and the AGM is governed by strict rules, etc.