Not sure if I've posted about this before, but this years
Hyper Japan festival in London, from 10-12 July, seems very surprising, since it's at the O2, and seems to be a much bigger event than before, and actually has a lot of performers!
http://hyperjapan.co.uk/Idol groups announced so far are: Dempagumi Inc, Tokyo Girls Style, Heisei Kotohime and Honey Spice. They will each perform twice, on the Saturday 1st session and on Sunday. There are some other Japanese acts like Eir Aoi and May J.
But yeah, it seems like it's going to be more competition in terms of idol groups coming to Europe, in addition to that Japan Expo in Paris, which I believe is the weekend before.
Honey Spice were the act announced today, and I hadn't listened to them before, but Hyper Japan linked their 3rd one-man-live on youtube, which I've listened to and seems like it will be a lot of fun to go to:
I'm looking forward to the whole event, will be so strange to see idol groups in the UK!