I don't think we should allow historic buildings to fall into disrepair to save a few quid. 12bn isn't much in the grand scheme of things, especially when it's spent over a couple of decades.Just stop wasting huge amounts of tax payers money on stuff like the £12 Billion refurb of the Houses of parliament.
The official annual tax gap is around £30bn a year, for context, and some think it may be to three times that.