EBGB is open, yes. And what a lovely place it manages to be and remain! But it is a strictly day VFR-only field and procedures must be carefully respected - they have more than their share of local nimby's and the aerodrome's traffic zone was "cut out" from Brussels CTR with Brussels TMA immediately overhead at 1000'.
(check out
Recreatief Vliegveld Grimbergen - EBGB - Grimbergen Airfield, but it might be local language only (and that local language is NOT French, btw, it is Dutch))
Also, if flying in from the UK, make sure you can clear customs at EBGB, if it is possible at all it must be requested in advance.
One should be sure to have a good alternate - EBAW Deurne and EBCI Charleroi are both reasonably close to Brussels, and ILS equipped, but of course much more expensive, with mandatory handling and what not.
Compromise might be EBKT with minimal IFR equipment, but it is a good deal farther away, perhaps a 100 km or so by road.