Hi Nico,
Those are complicated buildings! Rather than 2D |I woukld suggest low relied to fill the space up. As Pete (Mr Spock) has said you can use Korroflute or plastic corrugated board - its generally aboyt 5mm thick, which will genrally show the jomts in the corrugations - which means that the buildings are planked!
Brick can be scoreed but OH! it is time consuming! Jacksons minatures (
http://www.jacksonsminiatures.com/ ) do some brick sheets which are very good (got the 1:24 page where they are shown).
The brick sheeo can be better mounted on my favourite PVC solid foam (
http://www.grandtline.com/architectural_parts/quarter inch/quarter_inch_arch_index.htm ) that comes in 8 ft x 4 ft sheets, and is used for exhibition signs and is a semi matt finish - don't get the gloss finish that is no good for our purpose.
Windows can be made from styrene strip, or use Grandt Line from the USA - they are not cheap though, they have some 1/24th scale stuff at
http://www.grandtline.com/architectural_parts/quarter inch/quarter_inch_arch_index.htm
I use Evo-stik as a glue and its good
Peter when you say evo-stik is this the ordinary glue or outdoor waterproof glue.