We've bought our flights to Bruxelles from Glasgow - £30 each, including taxes and check-in and all that jazz. It's on Ryanair, who are "cheep uz chups "obviously (it could cost us more to get to London from here). Sure, the aeroplane doesn't leave from the main Glagwegian airport, and sure, it lands about 45 kilometres south of Brussels proper ... but in each case there's a train that will get us where we need to go.
Eurostar isn't as cheap as I'd originally thought, unfortunately. £150 for a one way ticket on a Saturday, from Paris to London. On the other hand, I think it's only £90 for a return ticket ... go figure. Chris should also get a discount because of his Eurail pass, so that looks like what we will do. It's still extravagant, but how often do you get to go under the Channel in an underwater train? Doing 180 mph no less -- that's 300 kilometer per hour.
Which is fairly fast.