here. The full list of diferent sports is here.
On the basis that they surveyed (at least one 30 minutes session of at least moderate intensity per week) cycling ranks as the third most popular participation sport after swimming and football, but ahead of athletics. Cycling is more than twice as popular as golf, from which I gain some satisfaction.
It looks as though in 2009 1,880,0004 people cycled at least once a week (4.50% of the adult population), which is an increase from 4.26% a year earlier. The increase was almost entirely accounted for by men in their early 20's, and late 30's to early 60's. There was significant growth in cycling in the North East and South West of England. The proportion of cyclists engaging in competition or tuition is relatively stable, but club membership has increased.