Every UK operators fuel policy is approved by the CAA and every fuel policy I have read states that sector fuel should be carried unless there are good reasons to carry more. The AIC is saying that inbound to airfields such as LHR there IS a "sound operational reason" to carry more fuel, it is highly unlikely that your system is including that extra fuel in the basic calculation.
The CAA are not saying you MUST carry extra fuel they are suggesting that it would be a good idea in certain situations, the final decision rests, quite correctly, with the skipper. I've made mine and I'm happy with it.