Indeed but you originally argued that using net disposable, as opposed to gross, income would negatively impact lower income purchasers, which I would suggest is untrue.You can calculate the amount someone can borrow using any criteria you like but things happen that screw up the best laid plans and those things are more likely to cause people on low incomes to be unable to pay their mortgage.
Because we need to increase the supply of properties of all tenure types - including rental properties.Rather than increasing the mortgage rates to allow those buyers to compete with cash buyers, who are almost always investment buyers, why not introduce a 15% stamp duty on all property purchases where the purchaser is not an owner occupier.
Incidentally, it's not true that cash buyers are "almost always" investment buyers. Plenty of cash buyers are simply moving from one part of the country to another, downsizers, etc.