MADONNA was left so impressed with new songwriting partner JUSTIN TIMBERLAKE, she has invited the SexyBack singer to spend the summer with her in London.Timberlake recently spent a week with Madonna working on new tracks for her next album and admits they came up with some gems. He says, "We ended up with five or six really good (songs) - some unfinished, some finished and we’re gonna go back in July and work on some more stuff." Timberlake admits he was impressed with the way Madonna works: "Her ethic is kinda infectious in the studio. I was like, ‘I’m too slow, I’m too slow…’ She’s a workhorse and I’m just a fan… who tricked Madonna."