Had a similar experience in Morrisons when over organising the 90th birthday of my Mother, I was with my DD and her then partner, got to the checkout and was asked if I Was over 25, DD fell about laughing while translating for her partner.
Assistant got stroppy and asked for I.D. we all whipped out our Belgian I.D. cards, she said she could not understand them, DD asked if she could read English, more stroppy, supervisor arrived, was hautily handed the cards by the assistant who pointed out to her that DD and I's were in English.We got the wine.
DD still recounts the experience to friends here.