The N.A.O. (National Audit Office ) concludes that the UK is a NET contributor to the European Union of £13.8 billion each year!
Have a look at this Link. It is a report written by the national audit office – it is public information and available on the main website as are other interesting documents.
The national audit office is independent of government. they report to parliament. the reports are politically neutral. the N.A.O. was setup over 100 years ago to provide independent assessment of financial issues.
The point is while lots of different organisations argue about the amount of our contribution this one is based on official information, assessed by trained auditors.