Hi Beerdrinker
Link below gives all the information from the Met Office website. All observers must now be checked and maintain currency to comply with CAP746.
http://www.metoffice.gov.uk/aviation...rtraining.html
As for human observer RVR measurement - yes there are many airfields that don't have the investment in IRVR transmissometer systems so rely on someone (properly trained and cerificated)
to count the lights.
C