Re: Flying to Brussels
While Brussels will accept you at almost all times, I'd suggest that you look at the larger surrounding airports.
Both EBAW (a bit north), or EBCI (really, really south) are perfect alternatives, have IFR approaches and will cost you far less. EUR 25 should get you in and out plus approx EUR 10 per additional PAX.
Overnight tarmac parking is available at both places, hangaring depends on your negotiation skills with the private operators.