Online Market Research into UK Charities and their expenditure

General information for the business: How much of the money donated to a charity actually goes to the needy? How much is spent on admin or other?
Geographical areas: UK
Data to include: None.
All information is available online
Extra notes: UK Charities take donations and give to Charitable causes.
e.g. The British Red Cross state (redcross.org.uk) that 5% of their income is spent on admin. This leads you to believe that 95% if given to the needy. However, they go on to state that 21% of income is spent on generating voluntary contributions
In effect only 67% is given to the cause after other deductions....

I need to obtain a report detailing the top 100 charities in the UK and how much is given to their cause and how much income is spent on running the charity. Are their any charities that given 100% to their cause and how do they fund overheads and operating costs?