We spoke to WLRFM yesterday (sound file here) about some of the contentious issues with a market value based property tax. Using values will ensure that the quantum collected is not strictly linked to any costs associated with running a local authority.
In the past this was a huge problem, it was the reason our last property tax died off, and when it came to domestic rates, it was used as political fodder in the 1977 general election where its repeal swung the election.
There are alternatives, Site or Land value tax and to have the tax linked to costs of a local authority would be far better, but we are instead opting for the path which suits the Government most rather than those who pay it.