Matrix - ITA Software
might have to check LCC via their sites
I'd consider using AF from CDG (time and patience) as an option. Use ezeds when possible.
spend time in tripadvisor.com forums--they have air travel as well as country/city forums, too.
I would avoid London due to high taxes/fees leaving. Take a look at From 35 euros:* THALYS high-speed trains from Paris to Brussels to Amsterdam & Cologne for train options. He even has a section on taking the train to Morocco (w/ferry connection).
Keep in mind when you're dealing with Ryanair, easyjet, etc, that LCC have very strict policies for bags/check-in and fees to match. Met FA from Flybe--might want to check for GB departures.
I'd be looking at some otehr sources besides ASU--their prices are not as I expected. You might find more under the Delta Perks on travelnet.
TA folks can offer ideas for apts, which I would go for if you're 4 people.
Happy to see you as a non-lurker!