4 days winter break to romantic Paris from Thessaloniki with ryanair.com from 35,98 euros!!
For 0 euros check couchsurfing.org
Enough people to rent a flat? check airbnb.com it might get much cheaper and more cozy from hostels and hotels.
To and from Paris Beauvais airport
You can check the airport's website for more options.
Easiest option though is with the shuttle bus with a schedule tailored for your flight that takes approximately 75 minutes till Paris and costs 31,8 euros if you book it online. More info here: http://tickets.aeroportbeauvais.com/Information.aspx
-Don't think about it so much, prices get higher )
-Double check your hand luggage size according to the company's limitation!
-Remember to check in online and print your tickets!
-Check the public transportation website for tickets and travel passes here http://www.ratp.fr/en/ratp/r_61584/tickets/
-You might find this link useful ;) www.disneylandparis.fr