It's not necessarily facts and figures Stagger, but a few things.
The first wave has clearly swept through most of the country and infected a reasonable proportion. Most of the fatalities have been in groups identified by Wheeze and others.
They can be shielded going forward.
So even a full on second wave could not take out the numbers the first one did all other things being equal if those vulnerable are shielded the caveat being that the virus doesn't mutate to a more potent form.
For anyone now being infected and getting to the point of hospitalisation, treatments have been developed that mean the recovery rate is much better than it was in March/April and they will continue to find new ways of handling the virus even without a vaccine.
Social practices have changed and even if we gave the green light to everyone tomorrow, everyone will be behaving differently. Rate of spread will be less if distancing, hand washing, face coverings... have any effect.
Finally we have a large proportion of the population either with an inherent immunity, or an acquired immunity, so there will be at least some natural barrier reducing the effect of the any second wave.