Quick update. Been having a play with my camera - taken it apart (a Logitech Orbit one) and removed the IR filter - sandpaper on lens - not the best way but it seems ok - i've took some pictures of the process..

Once done, tried the cheap and cheerful, 3 strips of negative solution to block out all visible light. I actually cut the strips very small and then sandwiched between the sensor and the lens - works pretty well.

Then took a spare piece of acrylic I've got - only small, about 3 x 8 inches and started having a play with this thing they call Front DI.....

Stunned that it actually works! - there's lots of tweaking to do with the software though as it keeps picking up parts of my hand etc. I suspect that the best solution may be to provide additional IR light from a source either infront or the side. Dunno - need to spend time playing with it really I think.