Don't know if this helps, from AIC 100/2006 (Pink 103):
4 If pilots state that it is their intention to commence an instrument approach and the reported RVR is below the Absolute Minimum,
ATC will issue a warning message as follows:
‘(Callsign) you are advised that the current RVR/visibility is (number) metres which is below the absolute minimum for a (name)
approach to runway (number). What are your intentions?’
4.1 If pilots indicate that it is their intention to continue the approach below 1000 ft above aerodrome level, ATC will pass the
following message:
‘(Callsign) if you continue the approach and descend below 1000 ft above aerodrome level, it is believed that you will be
contravening UK legislation and I shall be required to report the facts, acknowledge’.
This will be followed, at the appropriate moment, with:
‘(Callsign) there is no known traffic to affect you making a (name) approach to runway (number)’.
Subsequently, ATC controllers will not issue a landing clearance but will use the following phraseology at the appropriate time:
‘(Callsign) runway visual range (number) metres, there is no known traffic to affect you landing, surface wind (number) degrees
(number (knots))’.