If you are trying to find the official figures then I would try
Government Budget reports
Office for Budget Responsibility Fiscal Outlook reports data sources and proceeds details.
The IFS Survey of UK tax system quotes the following from the Office for Budget Responsibility fiscal outlook March 2011 report data.
Sources of government revenue, 2011-12 forecasts
(Three sources of revenue that might qualify as money from investments.)
Interest and dividends £5.2 billion
Gross operating surplus, rent, other receipts & adjustments £21 billion
Other taxes and royalties £25.5 billion http://www.ifs.org.uk/bns/bn09.pdf