I went to see the Asterix exhibit when I was in London in May. I'd recommend it. It's less about Asterix than a biographical display of the life and work of Goscinny, of which Asterix is just one part. The complex story of his early life in Argentina and New York, and the amateur and professional drawings he did before settling down to being purely a writer, were particularly interesting. I also liked a clip of a televised interview in which he and Uderzo explain how they worked.