The size of bag you may get away with slightly but it's the weight of it at check in that I've been done with on several occasions
Well I'm a bit wary because Easyjet now have slightly different rules. They are saying as long as you keep within the size limit there is
no limit to the weight, as long as you can lift it into the overhead containers!!
A few years ago we got stung for 70 euros at Granada airport (with Ryanair) for having excess weight on cabin baggage. The thing was we weighed our bags before the outward journey and had between 2 and 3 kilos spare. While away we used some of the stuff we took and bought nothing so we concluded there was a local scam with deliberately faulty scales. Others were also being charged excess (to everyone's outrage) and eventually the police were called to warn us that we either accept or don't get on the flight. Written complaints were responded to with a standard reply about us having agreed to the rules beforehand - we capitulated (couldn't be arsed to pursue for 70 euros) and made a mental note to not use Ryanair again until it became obvious that mostly they are unbeatable deals
Anyway I digress, I guess we'll have to travel smaller but not lighter.