There's an interesting paper in the January issue of JASIST: Using the h-index to rank influential British researchers in information science and librarianship by Charles Oppenheim. This demonstrates that the leading researcher in the UK is my former colleague, Peter Willett - a fact that doesn't surprise me, although it will surprise those who have carried out citation studies and have used only the Social Science Citation Index - most of Peter's work is in chemoinformatics and information retrieval and much of his research is covered only by the Science Citation Index.
There are one points of argument in the paper, e.g., I am still research active, although retired, and Beaulieu is not yet retired, and, I think, still associated with the Department at Sheffield. I'd also be rather doubtful about including Harnad as an information scientist - he's a publicist for open access, but his research is in cognitive psychology.
However, read the paper and make up your own mind :-)