Hi Ulla
脱欧 just one of the reason. The changes to stamp duty introduced by the government in April 2016 are cooling on the buy-to-let market. Anyone buying a second home for any reason now has to pay a higher rate of stamp duty than someone buying a property that will be their main home.
Furthermore, since April 2017 landlords have to declare their rental income has started to change, meaning most will see their tax bills rise significantly. This change in tax relief only affects private landlords - people who own their properties as individuals (or couples), rather than through a business. My friend buy-to-lets property got very little profit now and looking to put his property back to market