Maybe I misunderstood Bodim. I thought s/he meant that the trolleys had a total of £15 in notes and coins, not just in coins.
I apologise if I was making a mountain out of a molehill, but on many squeezy flights I have taken the crew makes various attempts to address the issue - requesting exact change where possible, making announcements requesting change, promising to return with your change (and making a note on a handy napkin), etc.
Because this is such a frequent occurrence, at least on flights I have taken, I thought squeezy might have seen this as a hassle for their staff and an inconvenience to their customers. From responses it appears I was mistaken.
In my particular case I was at the point where the trolleys met in the middle of the cabin, I only had a £20 in UK currency, (which I had gotten from the ATM at Geneva airport, no other notes dispensed there) they would not take Swiss coins only notes, and I only wanted a beer. Neither trolly had enough change. They would take my Credit Card but would bill me in pounds not francs meaning high transaction fees. So I said, thank you but no thanks.