Hi,
My opinion for your queries:
If the total value mentioned in the Invoice is inclusive of Postal insurance then its better to mention that separately. It will bring down the actual cost of your mobile hence most likely to attract lesser duty, in case its subjected to.
The seller can use his own format for the Invoice. As its from UK so its most likely to be a printed one. Some figures may be hand written, that won't harm at all.
Better to have a copy of the Invoice by email for unwarranted situations.
I do not think an European seller will agree to mark the phone as used one in the Invoice when you have purchased it as new. Because, then technically he has to lie either in the Invoice or in the listing. He may not agree. Better not to try this at it may affect your image to the seller.
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Best Regards
๐
Swarup
Kolkata

.
Best Regards
๐
Swarup
Kolkata
