Given that there are so far three codes for different parts of East Sussex viz
Crowborough SV Framfield SR Rye KF
You may need to re-think your Q and ask for towns and counties, as some are clearly subdivided, and not at all sure that they are on physical counties eg KF probably covers parts of east sussex and Kent.
Anyway would love to see how the list pans out - so hope others post theirs !