I looked it up. According to their own data (see link at the bottom of http://www.guardian.co.uk/technology/2009/sep/02/ordnance-survey-business-model-costs-lea

I looked it up. According to their own data (see link at the bottom of http://www.guardian.co.uk/technology/2009/sep/02/ordnance-survey-business-model-costs-leak http://www.guardian.co.uk/technology/2009/sep/02/ordnance-su... - also this link is well worth a read), about 1/4 (£24.6m) it is publicly funded (tax money), while the other 3/4 (£68.7m) is self-funded (revenue from sales). However, the government probably gain more than they pay in terms of being able to use the data freely themselves (likely to be more than £24.6m if obtained from an outside source). So it is possible to consider the OS as more of a publicly-operated for-profit company than as a public-service.