@ProseccoOnTap the trouble with that is that land doesn't have the same value across Scotland either.
A big garden in Morningside is probably worth a lot. A big garden in rural Angus, not really.
Jeremy Corbyn proposed a garden tax didn't he but again it shows someone with a city focus.
I have an ex council house with a much bigger garden than other things locally but it doesn't add anything to the value of my house, it's still worth a lot less than the traditional cottages on the same street with tiny gardens.
The property market is so varied regionally that finding anything fair is going to be difficult. If you go off house value then areas that remain cheap (I think Angus was the last to have an average house price over £100k for example) are going to have a lot less revenue raised by their councils than areas where house prices are high.