Do We Pay Vat When Selling On Amazon And Do We Have Any Postage Requirements, Eg. Must Be 1st Class?

A Seller charges VAT ONLY if they are Registered for VAT (they are forced to Register if their turn-over exceeds about £60,000 in a year, but some Register voluntarily)
Buyers pay VAT to Sellers who are VAT registered (plainly, some are, some are not)
Books are ‘zero rated’ for VAT (you pay 0% on Books, 15% on everything else)
Amazon gives Sellers a ‘postage allowance’ .. this is adequate for 1st class ’signed for’ on standard paperbacks but does NOT cover the cost of posting technical manuals or anything else that’s heavy. Parcel Force restrict anything over 2 kg to 1st Class anyway.
If the Buyer reports the package has not arrived, and you failed to send ’signed for’ (= ‘Recorded Delivery’) too bad, you have to reimburse them .. Buyers know this and some play the system, claiming on everything that’s not signed for … (fortunately very few crooks steal books, possibly because they are too ill-educated to read ..)