There have been many discussions on the question of the legality of using a scanner - or any radio for that matter - to listen to ATC broadcasts.
Whilst to license is necessary, or even obtainable, I think you will find the following link to an earlier thread will answer all your unasked questions - there again it probably will leave you even more confused.
[URL=http://www.pprune.org/forums/showthread.php?threadid=151509&perpage=15&pagenumber=1]
Cheers
Scottie Dog