According to Transavia website (https://www.transavia.com/en-EU/service/hand-luggage/) and Vueling (http://www.vueling.com/en/vueling-services/prepare-your-trip/luggage) you're allowed to take 45x40x25 and 40x20x55 accordingly. Both sites say 10 kg max.

  Make sure it is only one piece, so no purse, no laptop bags, etc. allowed (put them inside the biggest one).

I have Samsonite small bag that sold with "cabin size" label (something like http://www.samsonite.co.uk/smarttop-upright-50cm/75135.html?dwvar_75135_color=1549&cgid=SAMS080#start=11), and I never had any problems to get on board.

According to Transavia website and Vueling you're allowed to take 45x40x25 and 40x20x55 accordingly. Both sites say 10 kg max. Make sure it is only one piece, so no purse, no laptop bags, etc. allowed (put them inside the biggest one).

I have Samsonite small bag that sold with "cabin size" label (something like this), and I never had any problems to get on board.