Will be staying in the 7th. and need to get to CDG Sunday morning - since we are in an apartment not a hotel am wondering if would be useful to book a car to pick us up and take to the airport or whether getting a taxi is easy on a small sidestreet?

I'd say book a shuttle. Cabs are not hailed in Paris, but rather taken from a cab stand. I know others on this forum have been in your situation, so I'll let the experts....

Last year I used Bee Shuttle to take my from my apartment in Paris to the airport. I would recommend it. Door to door service. http://www.beeshuttle.com/

no, it isn't easy to get a taxi on a small sidestreet, it's about impossible. Unless you just mean will they come there if you call, yes, but if you mean can you just walk out to the street and expect a taxi to come by and stop for you when you haven't called, no, they won't do that. You'd have to go to the official taxi stand nearest your apartment. A good map should have them on it, or perhaps you'll see it when you are there. There's no need to book a limo rather than a taxi, though.

Here are some taxi companies, list provided by Tourist Office:

http://www.parisinfo.com/paris_map/r...d_article=6761

Note that if you call for a cab, which I would do, the driver starts the meter when he heads in your direction.

http://www.taxis-bleus.com/A_index.html