Annual figures on research and development tax credits are published as National Statistics on the HMRC website:
http://www.hmrc.gov.uk/stats/corporate_tax/randdtcmenu.htm
The latest figures show that the numbers of claims under the SME scheme were 4,960 in 2005-06, 5,270 in 2006-07, and 5,930 in 2007-08, and the amounts claimed were £180 million, £200 million and £250 million respectively. Figures for 2008-09 are not yet available.