All fixed. The bug was in how I was building the postcode-to-council mapping.

The script was extracting prefixes from individual application addresses, and Ceredigion's database happened to have a chunk of records with HR* postcodes (data entry errors at source. The addresses are Welsh places like Aberystwyth and Borth, but with Hereford postcodes attached). Those errors polluted the lookup table, so HR* ended up pointing at Ceredigion.

Fixed by trusting only the manual postcode-to-council mappings for councils that have them, rather than supplementing from address extraction. The postcode you sent now correctly shows "not yet in coverage" rather than results from rural Wales. Cheers for flagging. That was a zinger of a bug.