Hmmm, for me this seventh video is the most interesting:
http://www.youtube.com/watch?v=5Dh0IqSgirw

It claims that since 1992 the Western Blot HIV test,' which is
consider the more 'accurate' has not been used in England.  I've done
a bit of Googling and there appears to be conflicting opinion.  Some
sites suggest that Western Blot is done if the initial ELISA test is
positive, however tucked away in a PDF document from the Health
Protection Agency I've found this:

"Within the UK, Western Blot (WB) testing is not routinely performed
and is restricted to specimens with atypical serological profiles
(weak or discordant), or where there are epidemiological factors which
suggest supplementary tests are appropriate."

(Report PER06015, titled Evaluation of  Fluorognost™ HIV-1 IFA)

And here: http://ourworld.compuserve.com/homepages/dp5/aids.htm

"In the US, a positive HIV diagnosis based on the Elisa test must be
confirmed by a Western Blot test. In the UK, diagnosis relies on
repeat tests with various types of Elisa, as the Western Blot is
regarded as too unreliable."