Jura, I don't have a clue is the honest answer. London estate agents are already struggling in some areas where prices have fallen by 10%. I don't know if that's Brexit or stamp duty changes, or if a fall in price is necessarily a bad thing.
People could stay where they are and extend their properties, so small builders might do well.
Change is always more complicated than we think and I'm sure some businesses will do very well and others will not. But that has happened anyway - there's always winners and losers. I do think that business owners are very adaptable though. They are all people who have seen an opportunity and invested their time and money to build a business. Whatever happens with Brexit, they'll still have that same attitude.