It would all depend if I was in a good mood or a bad mood if that happened to me. Bad mood I would have gone back into the store and asked for my £1 back. You have to ask is it the responsibility of the store to refund you for your loss as you hired the trolley from from them. Or is it your responsibility for loosing it. The VM syndrome in me would made me go back for a refund. Whether I got it or not would be a different story. I am a pensioner I can't afford to loose a £1 would probably work. I was in a store last year with the other half just having a look to see if there was anything we needed when one of the assistants came up and asked us if she could help. It was the middle of the winter so I said no it is al right dear it is just because our heating is not working and it was nice and warm in here so we came in for a heat. Oh you poor soul was the reply we have a little room over there where you can go and sit and warm up. No it's ok dear we were just going anyway thanks for the offer. I never had the heart to tell her that I was just kidding.
I notice that some stores are now selling disk's the shape of a £1.00 coin with a key ring attachment, that can be used on supermarket trolleys.
Perhaps a word of warning. If someone offer you a trolley in exchange for a £1.00 coin, then be a little cautious, because they may have used a metal disk the same shape as a £1.00 coin to release the trolley. This scam was recently being used in a couple of supermarkets in our area recently.