The problem of OOs having to compete with LLs in the housing market, combined with the low rate of building new homes can both be fixed with a very simple measure.
All homes (not student or other short term accommodation) in the PRS would be under a licencing system. No new licences would be issued, except for new build homes.
Done.
Investment funds for residential homes go entirely to fund new build, generating increased build rates. OOs don't have to compete with LLs for non new-build homes, increasing owner occupation, with more reasonable prices.
Another result, if LLs want to cash in capital gains, they can't sell to other LLs, as these homes are no longer new build, so the licences expire. This would dampen capital gains, as they would be selling into a more saturated market, thereby cooling the attraction, and therefore the volatility, of the investment side of the housing market.
Some tinkering would be needed on the details and what-ifs, but basically...
Ta-dah!
:-)