Ancestry.co.uk have recently put online Poll Books that are part of the London Metropolitan Archives holdings. Although held by a London based archive these poll books cover the UK. They mainly cover the time period 1832 – 1872, but some date back earlier.
Prior to 1872 voters had to declare publicly who they were voting for. There was much concern that voters could be bought by a candidate to ensure their success. These documents are well worth searching as it was not just the wealthy who could vote, tradesmen often appear amongst the list of voters.