The National Aids Trust is campaigning for opt out rather than opt in testing for high risk groups.
Not quite compulsory.

Expanded 'opt-out' HIV testing
It is important that testing efforts reach
those most at risk from HIV and, in
particular, those who would otherwise
be diagnosed late. To do this, the
UK must move from reliance on its
traditional 'opt-in' model of voluntary
HIV testing, usually conducted within
sexual health clinics, to a more 'opt-out'
approach (also known as provider-initiated testing) across a range of
healthcare settings. This is where an
HIV test is usually offered alongside
other routine tests; the patient can turn
down the offer, but must explicitly say
no. Opt-out testing in antenatal care
has already proved highly effective
in reducing mother-to-child HIV
transmission.
http://www.nat.org.uk/media/Files/Policy/2012/May-2012-Testing-Action-Plan.pdf