One of the comments on the X post that I linked to above mentions a EUR10 tax on flights under 500km from Belgium (BRU-BHX is apparently 467km), and there is a proposal to increase said tax to EUR50 - is this actually true...?!
Perhaps the route could work using a 70-seat turboprop (i.e. ATR72 or similar) although there is not an operator that could fulfil this currently; wasn't BHX-BRU previously operated by bmibaby and/or Flybe...?!