You can check your document for color problems with the Preflight panel (Window>Output>Preflight). Open the panel and choose Define Profiles from the panel flyout. There you can define a profile that will find any object that uses a color other than Black or your spot orange. So here I've defined a rule that doesn't allow any color space other than CMYK and Spot Color and doesn't allow the CMY plates—only 1 color plus Black.
If I turn on Preflight I'll get a list of violations. Here the top two rectangles pass but the bottom rectangle uses CMY in its mix.
Edit the document color until it passes the preflight test and then export using the default PDF/X-1a preset, which doesn't allow color that is not CMYK or spot.
And you can open the output preview window in Acrobat (similar to ID's Separations Preview), uncheck the black and spot orange boxes and see if anything is still visible in your PDF. CS5.5 is always going to include the CMY plates during export, but they may (in this case should) be blank.
Hiya Robert/Peter,Thank you so much for your responses. I've followed the instructions and have sent them the document, with luck they'll be able to use it. No matter how much i learn there's always some little bits of inDesign to get to know! thanks again
Quick update! they were fine with it and it's gone to print, so thanks again