Revised posting, revised 2nd August:
For some time, the UK Research Councils have been deliberating about whether researchers they fund should place their research into open access repositories. After a consultation, they have decided to leave the decision up to each individual research council.
The Medical Research Council will mandate researchers to place their publications into PubMed Central, from October 2006. The Economic and Social Research Council will encourage people to put their publications into the "ESRC awards and outputs repository" (I am not clear at this precise moment exactly what this is). The Biotechnology and Biological Sciences Research Council will require publications resulting from research that they fund to be put in an "appropriate e-print repository". For University of Leicester researchers, this "e-print repository" is Leicester Research Archive.
The other councils have yet to decide or are awaiting the results of a RCUK investigation into publishing as a whole.
You can read more about this in these places:
ScieCom Info (in Swedish) - this is a bulletin compiled by Ingegerd Rabow, project leader of Svenskt Resurscentrum for vetenskapelig kommunikation, based in Lund.
SPARC Open Access Newsletter
and on the RCUK website, which links to statements from each council.
and, in Science of 7th July and the BMJ of 14th July.
The ALPSP (Association of Learned and Professional Society Publishers) have responded to the RCUK statement, and you can read about it via the UK Serials Group's Serials e-news.