The latest cencus was in 2001. And accordiong to 2005 records UK population is 59.8 million. Next cencus will take place in 2011. And some other details which useful to know about Life in the UK test are

UK Population 2005

England : 50.1 million (%84 of the UK population)
Scotland : 5.1 million (%8 of the UK population)
Wales : 2.9 million (%5 of the UK population)
Northen Ireland : 1.7 million (%3 of the UK population)

What is the largest ethnic minorities in the UK are
Indian 1.1 million
Pakistani 0.7 million
Black Caribbean 0.6 million
Black African 0.5 million
Bangladeshi 0.3 million
Other Asian 0.2 million
Chinese 0.2 million