At what age does the average unattached British girl start panicing to find Mr. Right?

If a woman is single and not seeing anyone, at what age do you think the average woman in these circumstances begins to think I better get looking for Mr. Right. Keeping in mind the average length of courtship before engagement is about 18 months and most engagements are usuall 9 months to a year before a wedding date. Added together,then, you must figure a total investment of 2 and a half to 3 years of time from when dating begins to wedding day. So, I guess the average age of first marriage minus 3 or 3 years would be a pretty good indicator.