Travel from London to Belgium

National Express/Europline bus will do the route for about 45 euros, journey time about 8 hours. If you book well in advance at http://www.eurostar.com you can take the direct chunnel train in just under 2 hours at a similar price as the bus.

James, EasyJet flies to Amsterdam from Gatwick and may be cheaper than the Eurostar to Brussels + train to Amsterdam.

If you book far enough in advance (up to 120 days allowed) on the NS Hispeed site, you can get a fare as low as 50 EUR for London-Amsterdam. The London-Brussels leg is on a Eurostar train and the Brussels-Amsterdam leg is on an IC train.

Thanks. I have found a $60 ticket for Eurostar and I think I may go with that since this way it only takes 2 hours.