I think you’re thinking of a case in the USA that colluded on rental prices? I don’t know of any evidence that there is collusion on house prices in the UK. People separately talk about investment companies buying up housing in the US as if that will have much impact on prices, but the proportion of housing under discussion is miniscule and unlikely to have any effect on prices - at least, outside of limited areas.

I’m guessing at what you’re referring to here so feel free to get specific. But cases in the USA are not that relevant to the UK, where the government is far more willing to enforce free market conditions than the “free market” idiotlogues in America who think that you can have a free market without regulation.