Periodic Postcodes (Hard)

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Across
  1. 1. Colchester
  2. 7. Bath
  3. 9. Portsmouth
  4. 11. London West
  5. 12. Newcastle-upon-Tyne
  6. 13. Lancaster
  7. 14. St Albans
  8. 15. Harrogate
Down
  1. 1. Carlisle
  2. 2. Swindon
  3. 3. Cardiff
  4. 4. London South East
  5. 5. Birmingham
  6. 6. Bromley
  7. 8. London North
  8. 10. Sunderland