Perhaps you should have read further down the article then?
The quarterly index shows that the average "shoparound" premium – based on the three lowest quotes for a customer, which most closely resembles what buyers actually pay – accelerated steadily over the year, adding more than 22% to the typical comprehensive quote over the past 12 months. It ended the year at £613.
It seems new fleet is suddenly £387 more affordable. Your assumption that new fleet is recruiting under 25 males is just that - an assumption. Along with your assumption that they'll need to buy a car, and that it will cost them £1000 p.a. to insure. You are complaining that new fleet cannot afford a champagne lifestyle on lemonade wages. The answer is to live a lemonade lifestyle.
PS As you have quoted the average wage in London, compare that to the average semi-skilled labour wage in London here:
Semi Skilled Labourer Average Salary