In 2002 the Royal Mail issued a series of stamps with the title "Pillar to Post" to commemorate the 150th anniversary of the first pillar box. I thought I had the whole series of 5 as PHQ cards but the ones above are the only ones I can lay my hands on today.
Apart from these I found several from the Netherlands:
I believe there were several designs of the Postcrossing stamp, and I'm fairly sure I have had others but they must be filed in the same place as my pillar box stamp cards.
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