I think that the following is one of the better reports:
http://www.guardian.co.uk/uk/2012/jun/29/uk-floods-transport-power-homesI am not sure if the size of the hailstones is mentioned
in the above report, but they were the size of golfballs and smashed car windscreens, not pleasant.
The sky is a little less threatening today and I only expects to see a few showers but Wimbledon may see a few more.
I was lucky, our drainage systems coped with the deluge but other areas local to me did not cope as well, and there is extensive flooding and damage to a large number of properties.