Hi Mrs TrevJel,
Something else to consider is a picnic rug. We've only just picked up our camper, but plan on using the picnic rug that we used to use for our the tent. I managed to find it from Coles for ~$20 and is huge (i think around 2x3m) with vinyl backing. The trick is to get one big enough though, as most of them look good folded but are tiny when unfolded. In fact ours is too big, but we just fold it up at one end against the camper wall.
We prefer it over the rubber mats, as they take up a fair bit of room, and the rug feels kind of 'carpet'-ish under foot. At the end of the trip (or during) we just grab a corner each and take it outside to shake the dirt/sand off. It also takes the chill off the PVC floor. As for protection, even though it's not as thick as the mats, we aren't worried, as the use of shade cloth under the floor, plus a quick visual look over for sharp sticks etc when setting up is protection enough for us.
As for dust sealing, don't be disheartened if some dust gets in, as there's not a single camper out there that is fully sealed... and don't ever believe them if they say they are. Fine bull dust will get in. It's like the annoying in law who manages to show up uninvited at parties!
LJ