The only problem I can foresee with World Works Games would be if you bought one of their older 1.5" sets and needed 1" sets.
Otherwise, they are incredible. I own many of their sets, and mix and match things quite freely. They also are incredibly supportive on their forums of "kitbashing", which is taking something of theirs and mixing it around.
The other company I highly recommend is
Fat Dragon Games. They make some really good stuff too. I recommend starting with the E-Z Dungeons basic pack, and going from there.
I've tried a couple other companies' stuff, but I don't like it as much as these two. Since they both tend to use a 1" scale, it's fairly easy to pull a table from this set, and a chair from that set, and make it all look good.
If you've not done paper modeling before, realize that it can take a bit of time the first time around, but once you get good at it, it's a breeze, and the creations are awesome!
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