Lee
I have the same receiver - great coverage but rather poor audio quality I thought. Great for for listening to all the go-arounds at EGLL
whilst not aviating myself.
I did a search for UHF airband frequencies on Google and found a few sites with lists of (exclusively military) frequencies.
As to the legality of tuning in to these broadcasts...
EDIT: I found the built-in antenna pretty rubbish for reception (too short!) so purchased a replacement telescopic antenna online. Much better reception now!
Regards
Adam