It's all to do with the 'added value', hence the chocolate biscuits case - it's not that they are a 'luxury', it's that adding chocolate adds 'value'. The same with the orange juice, the act of squeezing it counts as performing an additional service, and renders it VAT liable. Therefore, by eating in the shop you are liable for VAT, because the shop is providing it's additional facilities for your use, ( though in effect the price is no different, they just have to account for 'eat-in' or 'take-away' on their till rolls, which is why Rotten Ronnie's and Kentucky Fried Rat ask you whether you are eating 'in' or 'out' ).