The Department of Trade and Industry's Promoting SET for Women Unit in the Office of Science and Technology has launched a new Web site  that attempts to bring together all the statistics currently available on UK women in science, engineering and technology (SET). The unit has already gathered statistics on the numbers and percentages of women active in science at various stages of education and employment, and they plan to add more as soon as they are available.
The data are presented as a series of tables showing how many women are involved in SET in school, further and higher education, publicly funded research, and employment. There is also a brief commentary associated with each set of data, although perhaps this could be expanded for the benefit of those whose eyes glaze over at the site of too many numbers. The intention is that the data will be added to over time to "build up an archive showing changes in the pool of SET skilled and experienced women."
But don't expect to find the answers to all of your questions. Some important data just don't exist. The developers of the site acknowledge, for example, that there's a shortage of information about women scientists employed outside of academia.
The site also highlights inconsistencies in the type of data collected by the research councils. The Medical Research Council provides by far the most comprehensive data, giving absolute numbers of awards and the percentage of successful applications from men and women. By contrast, the Engineering and Physical Sciences Research Council gives absolute numbers of awards, but not the success rate, and the Biotechnology and Biological Sciences Research Council provides the success rate but not absolute numbers! While this may sound like nit-picking, in 1997 the Wellcome Trust found  that, though women applying for its grants are just as likely as men to receive awards, fewer women than expected were applying for project or programme grants. The reasons for the dearth of female applicants are currently being investigated, but figures like these are worth keeping an eye on.
It has to be admitted that this site is not a right, riveting read. BUT, it is a useful one-stop shop for locating distaff-side digits.