Hi the plastic windows on my camper were looking rather murky and misty I somewhere read about using wd40 to clean them. As we had the canvas off after it had a new zip we gave it a go very cautiously. We sprayed it onto kitchen roll then rubbed the windows - both sides and used a clean tea towel to make sure we removed it fully and I have to say they are like new, crystal clear it's made such a difference.
I might give that a go. We purchased a used camplet. It's in fab condition but the previous owner ad sprayed waterproofing onto the canvas and it's run down the windows and we can't lean them properly.
Liquid wax car polish brings them up a treat, I got waterproofer all over the windows of our Vango tent, and I'd tried everything to shift it, but it wouldn't budge. Then I gave them a clean with car polish and they were like new, with the added bonus that when it rained the water ran straight off, keeping them nice and clear.
------------- Camping is not just a holiday or short break, its a way of life!!