Unlikely anywhere near the number of the most vulnerable are already dead. There have been about 45,000 deaths at least partially attributed to COVID. There are almost 8.8 million people over 70 (the most vulnerable age group) in the UK. Plenty more fragile people for the virus to propagate and kill. That is not including the remainder of people who are younger but have underlying health conditions that makes them vulnerable.
The UK has a lot of people who aren't in great health. That is why the NHS is expensive to fund, and not matter how much is spent on it, it never seems to be enough.
But being cruel .....how many old people are simply kept alive due to drugs / medication, and have no quality of life ? as late as the 80's to reach 90 would have been rare