No. Leo and Scorpio both ascend slightly quicker than Virgo and Libra, though the difference is not very great. So I can't follow your logic. It is the 30 degree movement from 15 Virgo to 15 Libra that is slowest. The 30 degree movement from 15 Pisces to 15 Aries is quickest.All of the signs ascend at regular and predictable times and Libra moves at a similar speed to Virgo, and by your logic the most common ascending signs should be Leo and Scorpio.
Again, I never suggested that there would be more people born under the "slower" ascendants, world-wide, since close to the tropics the differece in times are greatly minimimized, and everything is reverse in the southern hemisphere.
However, a study done ONLY for the UK might yield interesting and unexpected results.