Apropos of only voting if you pay income tax.

I felt sure this must have been considered in the voting reforms of 1832, 1872, 1918 and others. This led me to a very good summary of the changes in The History of the Parliamentary Franchise from the House of Commons library. And all the debates have been scanned and can be read at Hansard Millbank Systems, which I admit surprised me a bit. Unfortunately they are simply scans, so they are not easy to browse: you have to go by page number, not date, for example. You are invited to try your luck.

Paying income tax is broadly similar to the pre 1832 scot and lot qualification:

"The scot and lot qualification was based on the householder’s payment (scot) of a share (lot) of local poor and church rates. The potwalloper qualification was a householder who was self-sustaining (they made no claim on poor relief) and who had their own hearth on which they could cook or boil (wallop) a pot."

Suffice it to say that Parliament decided that was not the right way of determining who could and who could not vote.