If you are looking at train travel as an option, check http://www.bahn.de/i/view/GBR/en/index.shtml
carefully. I know it's been mentioned already, but you might not know that you can input any UK station (as well as pretty much any station in Europe and any German address) as a starting point to find good connections. (How clever!)
It's also often worth checking to see if you can book differing parts of your journey through Deutsche Bahn, as they *could* be cheaper than Eurostar, who are often mega rip-off merchants.
Adjective: Fat, round, or bulging.