The approaches into Heathrow were changed slightly after 11 Sept for a brief period to avoid overflying parts of London. However, that was for only a few days and things are now back to normal and the approach paths from Biggin are the same as they have always been. The Biggin holding area is as busy as the other three Heathrow holds but traffic levels vary during the day. Sometimes we'll have 20+ minutes delay; at other times there will be very litle traffic offering. That said, our overall levels are only marginally down on those prior to 11 Sept.
You should have noticed considerable holding in the last few days due to the dreadful weather..
Hope this helps...