Pontoise and Toussus are the two usual ones for Paris.
However, I don't think "Paris for lunch" is terribly practical unless you make an early start; I went to Pontoise last year and it took us 2-3 hrs to get into "Paris", using public transport. A taxi would be quicker but probably very pricey (Deauville got a name for ripoff taxis).
Antwerp EBAW was not really expensive (2009) - under 100 euros total. Brussels EBBR... you can phone up some of the handlers there but it is likely to be ~ 200-400 euros, along with Frankfurt and Munich.
There is a lot in near Europe to see; great value for day trips (if you live on the south coast) and overnight trips otherwise.