I dont think the management of LTN will be losing much sleep over the loss of a BMI regional service to Brussels.
Definitely NOT! It would only have lasted 12 to 18 months anyway, after all, once the Eurostar terminal is opened at St Pancras Intl., in 2007, why would anyone who can access that station from for example, North London, Beds or Herts., choose to fly LTN/BRU when they can do the journey via Eurostar to Brussels' City Centre?
This must also bring into question, easyJet's LTN/CDG service...??
But some additional services from LTN into Germany and Scandinavia - now that's a different matter and these are two areas that are currently, not well served.