The staff in the Business Premier lounge can also sort seat requests for future trains. Doesn't help if you need to switch tomorrow's seat on a ticket booked with Loco2 / SNCB / etc, but can be handy if you need to do it for next week's / the return leg.

I've heard a lot of people grumbling that the first London to Brussels train of the day gets them into Brussels too late for their first meeting, due to the time difference. I wonder if the re-timing is based on feedback from people struggling to make a 9am monday meeting in Brussels?