Also, of course, the flats have an entrance onto Blah Drive but have addresses in what I always think of as being Cunnilingus Close but isn't, quite. The flats are numbered contiguously with the houses i.e. 1 to 10 are houses, 11 to 30 are flats (though one flat has its own front door rather than communal entrances and one doesn't exist) and 31 to 75 or thereabouts are houses.
Conversely, there are houses that face Blah Drive which have numbers on Blah Drive though you get to them via side roads, in a couple of cases you have to go quite a way into the side road to get to them, but they face Blah Drive so they have numbers on it seems to be the rule. Also, whilst all the side roads have houses numbered consecutively round the side roads, the houses on the the main road are scrupulously numbered with even ones on one side (and possibly odd ones on the other, though those too can only be got to by going deep into another side road).
Also, one of the roads has no 40 but has a 39A. There is a factoid that 40 is unlucky in China as well as 4, so maybe that's why.