I have recently heard of the iDBUS which is now being run by the French national railway SNCF as a bus alternative between Paris and London, and London and Amsterdam at some fairly reasonable prices - starting at £24 ow pp London Paris, £21 ow pp London Amsterdam.
I guess that this is competition with the Eurobus and Polish bus options on the routes.
iDBus sounds like a take on the iDTGV that they run with the TGVs in France.