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It doesn't look like you can.

From the FAQ on your Maplin page:-

Q) Could I use this to connect the Component Output from Apple TV to my Sony Widescreen CRT? - Phil
A) Unfortunately not. This does not convert Component signals into a Scart Source, it converts Scart Source into Component signals for use with items that require Component input.

Q) If the three outputs are for RGB and the fourth for projector sync, what about audio? - James
A) This product does not support audio.
 
What you need is a converter box from JS Technology (www.js-technology.com). Costs about a hundred quid and it will convert the component and audio outputs of the appleTV into a SCART signal that old-style TVs can use (in my case an 6-year old 28" JVC CRT television). Box comes with converter, power lead and all the appleTV-specific instructions you need and you just add your own TV and interconnect cables. UK-based and the blokes there were very helpful when I spoke to them. Best of luck!
 
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