I just got shown what to do and it's so going to stop the panic search for a £1 coin. So simple and brilliant.
Take a key off your key ring. One that is a circle at the top 🔑 like this.
Stick it in the coin slot. It releases the trolley. Take the key back out put back on your key ring and happy shopping.
Aldi have locked their trolleys again and I just saw someone do it who didn't have a £1 on her.