That wasn't their house. They had been sent to the professor's house to stay as the blitz was going on, so London, where they actually lived, wasn't the safest place.

If you’re talking about the wardrobe they find Narnia in, that’s not their house. The the house of the old, rich professor they are staying with in the countryside, safe from the bombings during the war. The Pevensies themselves are meant to be like middle class I think

Gentle reminder that slave labor, industrial automation and exploitation of far away lands were not even recent in 1950, and that still today, the vast majority of humanity still doesn’t have the means to own hundreds of outfits at a given time, let alone have a walk-in wardrobe.