The amount of houses being bought by foreign buyers is ridiculous, especially in London. This is a big reason why house prices are out of reach. Yes, foreign money does help housebuilders, as houses are being built but it's only really helping building firms pocket higher returns, and making young people to own a home further out of reach. This is why there are also so many properties that are empty because London properties are a safe haven for foreigners.
The best way is to tax these foreigners when they buy and sell UK houses and also increase the council tax on them. If these foreigners are buying through a company higher tax should be placed on them as well.