Absolute minima has nothing to do with Cat 1, Cat 2 etc. Absolute minima is connected to the landing runway. Each runway in the UK has an absolute minima. As controllers you should know what that minima is for your landing runway. If an aircraft passes the 1000 ft point when the RVR is below the absolute minima it is your duty to report this to the CAA.
This directly contradicts the advice to ATC in ATSIN no 19, which says:
There is no requirement to calculate Absolute Minima for Category II/III approaches, nor to pass a warning to pilots conducting such approaches, for which specific procedures for use by the flight crew will have been approved.