No1. Are they not expecting immigrants to age?
No2. A smaller population in the UK is a great thing, the UK already doesn't produce enough food to sustain the current population, they currently get 50% from abroad, the infrastructure can't cope with the current population and the proposed building of a million more houses will be devastating to the environment and wildlife of the UK.
No3. The excuse that the UK needs immigrants to look after the old is nonsense. Apart from the fact that there are millions of unemployed already in the UK, the unemployment rate is going to grow massively over the next few decades as people are replaced by machines, robots and drones, which is already well underway, those unemployed will get jobs looking after the ageing population.
http://www.bbc.co.uk/news/uk-politics-39729595
http://www.bbc.co.uk/news/uk-england-34209027
https://www.theguardian.com/environment/2016/jan/06/more-than-half-of-uks-food-sourced-from-abroad-study-finds
https://www.theguardian.com/business/2012/feb/14/uk-unemployment-underemployed-tuc
https://www.theguardian.com/business/live/2016/nov/16/uk-unemployment-rate-wage-growth-earnings-brexit-business-live
http://www.bbc.co.uk/news/uk-politics-35737104
https://www.theguardian.com/technology/2017/feb/16/self-driving-trucks-automation-jobs-trucking-industry
https://www.theguardian.com/technology/2016/dec/14/amazon-claims-first-successful-prime-air-drone-delivery
