I've just looked at my (quite old) 206 - still the silver one. There is a similar problem if you really look hard, but I left it at that. After fit, the body and the floorpan split a bit as the body curves outwards for that nice and bulky part around both front and rear wheels. The floorpan just goes straight on.
My decision was to leave it at that. If you don't do a wheel-off diorama, you won't notice it without turning the model over and squinting past the wheels. So if that's the same prob, which it seems, it is the case, yes. Strange they did not improve it through the years - mine is the 2000 Monte version, the year Gronholm won his first champ.
It all depends on what you want from the kit. But if it's a "serious" (or competition) kit, I'd advise the same as nicholma above. It should not be too difficult to curve out the bottom of the pan and widen it on the wheel arches. That is if you're staying in a place where can actually FIND styrene!
Having gone on about that - I've just picked up my (even older) McRae Subaru, also quite bulky over the wheels... same prob. The Lancer seems much better, but also not a perfect fit.