In an article Search clients by postcode I started a different discussion, so moved the details to this request.
@Glenn mentioned that “I think for those postcode areas that span across England and Wales (e.g. CH), we decided to take a more risk averse approach and just show a Union Jack. It’s very delicate ground and I’m sure if we had more granularity we’d be making a rod for our own back”
Reply @alan_mcbrien “The cross border postcodes seems to be defined for the use of different use of flag for SY Shrewsbury as Aberystwyth gets a welsh dragon for SY23, but not for CH areas. CH1, CH2, CH3 in England; CH4 in both England & Wales; CH5, CH6, CH7 & CH8 in Wales and then there are CH60’s on the Wirral. Can the Flintshire postcode areas be corrected?”