The legislation is there to protect individuals identity and voting choice if a small number of people vote at a given polling station. We have some polling stations in rural areas where only 9 or 10 people vote (and that being the total number of people in that community, say in Scotland or Wales) publishing data at that level would in principle reveal the vote of each individual (or make it very easy to ascertain) and given that voting in the UK is cast, by legislation, as a secret ballot, it would be illegal and a breach of the law (and probably some tangential extrapolations of the Data Protection Act) to publish something that by nature can be easily back engineered to the voting choice of individuals.