I tried a few Heathrow inbounds on it last night and it wouldn't list any when I used the full flight number. However, if you just feed in the numbers, ie "123" for "BA123" it comes up with everything with 123 in it's flight number, then you can just choose. I tried several of the graphics features but they locked up my PC so bad I had to re-boot!!
Interesting though.. but I doubt if it is strictly UK-legal if it's information is derived from Mode S..