DB IC Bus now run an overnight service from London to Düsseldorf via Antwerp and Eindhoven, leaving Düsseldorf on Thursday, Friday and Saturday nights and London on Friday, Saturday and Sunday nights. This service previously ran as a trial in December/January but now appears to be permanent starting on 21 May:
http://www.bahn.com/i/view/GBR/en/prices/europe/ic-bus.shtml
Fares to/from London start at 29 euro each way with a discount for BahnCard 25s.
http://www.bahn.com/i/view/GBR/en/prices/europe/ic-bus.shtml
Fares to/from London start at 29 euro each way with a discount for BahnCard 25s.