There are a variety of funding opportunities open to researchers to bid for. The providers of this funding include charitable organisations, Research Councils and the National Institute for Health Research (NIHR).
Below is a selection of only a few of the funding sources and search engines:
RD Info http://www.rdinfo.org.uk
Research Professional http://www.researchresearch.com/
NIHR Central Commissioning Facility http://www.ccf.nihr.ac.uk/Pages/Home.aspx
Wellcome Trust http://www.wellcome.ac.uk/Funding/index.htm
Medical Research Council http://www.mrc.ac.uk/funding/