I stumbled across the London Speaker Bureau just now. A pretty impressive roster of speakers just for you. It would have been interesting to know how much they cost. Here is a note on Bob Geldof:

Sir Bob Geldof is an influential and inspiring speaker. He is highly entertaining and has great insight into the sociopolitical and upliftment arenas and is highly sought after by companies who wish to benefit from his sensational presentations. [Bob Geldof - The London Speaker Bureau]