A very quick fix, but at some point in history my Chrysler Grand Voyager lost the cover to the cabin filter. On my right hand drive it's on the passenger side, under glove box towards the centre console. It's supposed to have a semi transparent white cover I believe, and mine doesn't! This causes cold air to blast down into the passenger foot well and stop the heater blasting out warm air elsewhere.

Well not to worry, a bit of cheap pipe insulation (QinteQ patented solution for winterising the gv!) cut to length does the job perfectly :

 

They always get snapped, scrappy or as you have done improvise Andy.