Adrion
There is still a post box here, but the post office has moved to inside WHSmith , 219 High Street, BN7 2AF, at the back of the store approx. Lat 50.87435 Lon 0.01517
I don't know how to tag this in the most useful way, so I hope someone experienced can do it. Thanks!

(PS. The Google map given by the Post Office website branch finder gives a slightly incorrect location.)