hey, If i'm right the 225 is the width...you should be fine i think....i run 235 40 18. looks great and gives me a bit more cushioning to ride on. i used the calculator thing months ago to help me figure it out.(what a great idea that thing is, i was pulling whats left of my hair out at the time.)
The 235 i run gives me a bit of a 'lip' where the tyre is wider than the wheel, so it protects against kirbing. there have been loads of times i thought i would kirb my wheels but this size tyre just does'nt let it happen.(within reason of course)
I think it will depend on your offset mate and how low the van is. mine is dropped around 50-60 mm and when i have had it loaded up. (et 35 )i did get some rubbing as the wheel jumps up into the wheel arch on the back. I'm getting the arches rolled out at the moment.
The guys at totallyt4 run an interesting tyre, might be worth checking out. i have recently seen them on a van they are working on and they are pretty cool. You get the lip, but the tyre width seems pretty narrow, hard to explain. ......hope something in there helps.