I was told by a man from the CAA that that the UK AIP is the only definitive source; and failure to depict, or ambiguous depiction, on a chart is no excuse. He implied (in pre GPS/digital/moving map days) that my gliding club should have a paper copy (all 5 thick volumes) of the UKAIP, use only that to verify where we could fly, and not rely upon charts.
That sounds like the CAA and they haven't changed much...
However I must admit I didn't know that the CAA charts contain systematic long term errors like this.