cshaun: Yeah probably would be a good idea 'walling' it up. I closed off the side vent with some plastic sheeting from a takeaways container... Though didn't realize at the time the vent by the PSU was longer than the PSU and is now sucking in air.
Those two case fans are surprisingly loud... Corsair PSU far quieter.
I used an ice cream container for the one by CPU. The case fan attached to the speed controlled MoBo header is quiet enough. I've been thinking about closing up the one by the PSU, but haven't done so yet.