I think a HST between Schiphol and (really) Brussels would be excellent. I just checked klm.com for GLA-(AMS)-BRU and I get the option of an F50 link to BRU or a train link to ZWE (then I'd have to get from Antwerp to Brussels under my own steam). The trouble at the moment is that the fare with AMS-BRU (> £500) is three times that with the AMS-ZWE (~£170), but the only GLA-AMS-ZWE schedule offered leaves GLA on the 05:55 (KL1470) flight (which seems very odd - surely KL can get a 27xx code share on more than one train per day).
-- H