I typed a long answer but think my PC may have crashed as I sent it, (so hopefully this gets through)
I
think you'll be dealing with a couple of issues. (1) The actual setup of
your BS2 and (2) the scart to component/composite issue. The ATV1 only gives
"component out" natively and I believe all scarts on the BS2 are composite?
Someone will correct me if I'm wrong. Assuming I'm correct -
First you need to get the picture & sound to come on screen - it will be black & white. My ATV1 is set up on my Beovision5 and in the settings menu V.TAPE was set to STB (V.AUX) and I had to add V.AUX to my Beo4.
Make sure your scart to composite adaptor is an "input" one and not an "output" one ie the 3 coloured sockets "input" to the scart. (You can get input & output types and switched models which make setup easier.)
On the adaptor connect the red & white to the Adio L&R on the ATV1 and the yellow to the green on the ATV1. Ensure the scart is pressed well into the TV as they can sometimes not sit properly. Now when you turn on you should see the black & white picture from the ATV.
I then bought this (aTV Flash) to get the coulour fix. Once installed you will see the instructions on their website how to enable colour via composite, follow the instructions, turn off & on and Voila - it works.
Or you can try this free fix which is what I used initially. (like the author of that thread I found that info on http://www.appletvhacks.net/ and know it works.)
Good luck
Stoobie