The joker in the pack is going to be what happens to the houses bought by speculators that are going to be hemorrhaging money each month as the section 24 rules taper in
https://www.noagent.co.uk/section-24-tax-relief-change-landlords/.
I'm seeing houses slowly drop in value in my old hometown of Kidlington Oxfordshire, the people who want to buy property as a home can't afford the current prices inflated by the speculators and the people who bought them as speculative investments aren't making capital appreciation or monthly yield.
We haven't reached the full effects of section 24 and won't until 2020, imo it's going to be absolute carnage (especially in the south) as most southern property is still a long way from being affordable for most ordinary buyers.