When Easyjet changed it’s guaranteed cabin bag size to 50cm x 40 x 20 it caused some anxiety, I think the confusion arose over the word guaranteed.
You can still take bags up to 56cm x 45 x 25 but on a full flight you may be told it has to go in the hold.
Many people were concerned that they would be asked to pay for this but it will be done free of charge- the only cost to the passenger is the extra time waiting for baggage retrieval.
When we travelled to Portugal on a full flight we were fine and no one questioned or even looked at our hand luggage.
I had a long conversation with a very worried Mother who had bought one of our Vaude Bags for her young daughter which was 1 cm too high. She was really anxious that it would be taken away from her daughter at the gate which would have caused much distress! Particularly as it was stuffed full of things to occupy her on the journey.
They called on their return and said it had been absolutely fine- Phew!! Since then Vaude have reduced the size of the bags by 2 cm- so no problem