looking for a house to share near BSB/ African Museum.

Your options are pretty much restricted to sticking a note up on the British School notice board. Personally, I wouldn't be inclined to share my house to a random stranger for an unspecified reason at less than a week's notice.
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At this sort of notice, you want to be looking at a B&B, and hope they have a place.
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Google Maps gives 2 options:
1. LeoLodge
Oude Leuvensebaan 12, 3080 Tervuren (Tervueren), Belgium +32 2 325 89 05 ‎
2. Hotel La Vignette
Leuvensesteenweg 12, 1970 Wezembeek-Oppem, Belgium
+32 2 767 83 56 ‎