Well, I can't recognize a single one of the stores you've been mentioning, but here in Spain it's not very different from what you describe. Plus size clothing is a nightmare: you will either find florals everywhere (like I need that), or those pregnant-looking tops you mentioned above. Nothing fits correctly, it's either baggy or too tight, and whatever fits my hips is huge around my thighs, etc... In the end almost everything makes me end up looking like a circus tent.
Then again, I have very skinny friends who say it's not a piece of cake for them either.