UK is already over-populated. I don't know where your idea of it peaking 'soon' comes from - whatever period of time that may be; nor do I know what you have in mind as a cause of the 'regression'.
I also find it wrong to keep laying emphasis on the number of older people who keep on living as if they were a plague upon us.
In part, a good NHS has allowed that but also it is true that many older people have reached their age because they have lived their lives in a healthy way and taken care not to get into risky activities.