Oxford University's Department of Economics concurs.

Emailed in by TBH, from page 29 of this:

If one is interested in the spread of owner-occupation per se, it is necessary to consider not only the two million plus houses built in the interwar period for owner-occupation, but also the large number of houses – estimated to be in excess of one million – transferred out of the privately-rented sector by sale to owner-occupiers.

In a large proportion of these cases, landlords sold their properties in response to the low returns imposed on them by the rent restriction legislation. (Conversely, they were concentrated in the 1920s.) In many cases they could only realise low prices for their properties, and they often sold to the sitting tenants.

Although there is little information on these sales – Merrett refers to them as the ‘hidden history’ of the interwar period – it is likely that many of them involved working-class households. In other words, many more working-class households became owner-occupiers in the interwar period than Swenarton and Taylor allow, not only because they bought many of the new houses built during the 1930s, but also because they also bought a significant number of pre-war houses, particularly during the 1920s.