Premium First also used to allow you to convert the ticket to a British Midland/BMI C class segment if it was more convenient to take an airplane on your return due to changes or rescheduling. This is no longer the case.
Also all the Eurostar rolling stock interiors REALLY do need a make over. This has been planned for some time now. Seems like this will be done by the end of 2004, there is also a proposed WLAN access on the trains + a supposed chunnel access for mobile networks by 2007.