It is very possible that only reason that "The question is less about how many people have been able to get homes, but how many will still be in them when they retire - never mind owning them outright ..." may be because the same policy frameworks that allowed people to get into such high levels of home ownership or housing quality/space per person (for renters) is due to the less regulated lending environment in the first place, so you can't honestly approach the issue without accounting for the possible benefits first, somehow.

There are two ways to do it that come to mind: One is to find data which shows that the benefits were actually quite low and the costs of the crisis high, especially to the most vulnerable people.  Another way is to show that the proposed policy changes would probably not have reduced the benefits people have enjoyed had they been in place already.  I haven't seen anyone address something like either of these questions yet, buy let me know if you have.