I bought some ice packs in Sainsbury's advertised at 70% off and was charged full price. I went straight to customer service and got my £2.10 back, might seem petty but it was my £2.10.
Greggs have a kiosk/stall in the indoor shopping centre selling drinks and pasties.
I bought a hot sausage roll for 80p (a little expensive I thought). Then I came across Greggs shop - same thing priced 68p. Asked the reason why and was told that the kiosk is classed as a restaurant therefore VAT is applied.