Just as an update.
I went into my local Post Office to post one of our products using the International tracked and signed for service. On the Post Office’s own website it clearly states that this particular service is “exempt” from VAT. However, once again the printed vat invoice clearly stated that this was “Zero VAT”. I queried this with the postmaster who confirmed there is no manual input with regard to VAT required. Their system does it all automatically. Interestingly I was also dropping off a on-line purchase return with a pre-paid return label. My receipt for that transaction clearly showed VAT as “exempt”.
I fully appreciate that this point is mute as both Zero VAT and Exempt have the same impact on my VAT return. Just seems to be very inconsistent that Royal Mail clearly state “exempt” on their website but their system prints out an incorrect VAT invoice quoting “Zero VAT” or am I missing something?