Obviously you can't ask for individual tax records (other than your own). What you can ask for are aggregate figures e.g. average values for a given area. This is similar to the newspapers getting LC exam results per school under FoI, without seeing individual student records. FoI is not just for access to your own personal information, it covers all information gathered by public bodies. Granted they may have an out if they don't already generate these aggregates, but I expect they do, in order to identify "suspect" valuations. Though I accept correctly wording a request to get useful aggregates could be difficult.