Recently flyed over UK and back on holiday and used Ryanair, Flybe and Easyjet without a problem. Had only one problem with security and the toiletry bag. They said it was to big and handed the usual bags, which was enough for me.
The only downside is that the materials are not very good and the same thing can be said to the sewing. It's not a problem near the handles (where it will be more strained), but all the other places (ie. near pockets) is very bad. Near the first front pocket there is already a little tear (between orange and zipper). I'm not sure if it was me or was delivered already like this, but I'm pretty sure I didn't strained the bag to give up so easily.
I'm not returning, because first is used and is to little for the effort. I'm gonna try and fix it myself so it doesn't get bigger.
In the end you get what you paid, cheap max cabin sized backpack.