The relevant section of the UK AIP states:
3.3.2 IMC Rating Holder in Current Practice
3.3.2.1 Pilots with a valid Instrument Meteorological Conditions (IMC) Rating are recommended to add 200 ft to the minimum applicable DH/MDH, but with absolute minima of 500 ft for a precision approach and 600 ft for a non-precision approach.
This is a somewhat ambiguous statement. As I read it, it is a mere recommendation and is sufficiently vague for any lawyer to successfully defend anyone using lower limits routinely. For example, it seems to state that it recommends that, where a published DH is 260 ft, the recommendation is not for 460 ft (DH+200) but 500 ft.
This is why my recommendation for the Class 2 IR uses mandatory additions to DA/H and MDA/H rather than the slackly worded statements above.Regarding industry 'best practice', most people I know use the simple figures published in Pooley's Guide as their everyday minima.
Thus industry has found a sound, commonsense solution which is easier to understand than the AIP! This could work to our advantage as it shows that the UK routinely provides sensible recommendations for 'amateur' pilots to follow - who would perhaps otherwise be confused by the AIP.