Re: Too much tax.
Well, this isn't wholly and exactly true:
"The principal problem with building new stuff is that it reduces the price of nearby existing stock"
I have looked... And I can't find a single instance where building a new build housing estate next to existing housing has had a positive influence upon the value of the existing housing.
I can find some solid examples of the opposite being true though. Take a look at Baldock in north herts. Its about to double in size in terms of dwellings. Your theory holds that all these people wanting to live there should increase the value of the existing property in Baldock. My theory is that it won't, and will in fact, reduce the value of the existing dwellings - possibly quite substantially so.
Perhaps you'd care to wager £30 to charity on the direction in which that moves prices?