The staff in the census office.
Correct. You might also add:
Civil Service - about 0.5m staff
Armed Forces - about 0.25m staff
Police and other emergency services - about 100,000 staff?
Local Government staff - 2.4m staff
NHS - 1.8m staff
and an unquantified number of hangers-on, QUANGOS, several parts of banks, and around 15% of the EU budget (2009 contribution was £3.8 bn)