Concealed drainage works by drilling a slot through the pvc section, when water builds up under the dgu's it will run to these slots, through an enclosed chamber within the pvc profile and out over the cill, do not seal the window across the bottom, this will block any drainage you have and to be honest it doesn't look like you have a gap between the window and the grey timber surround, i'd be a little concerned now.
Have a look here,
http://www.gjbdevelopments.co.uk/products.asp
its the best picture i can find, scroll down to tilt and turn, ignore the extra sections other than the cill and bottom window section, note the over hang of the window onto the cill, this is the gap you need, now imagine a slot drilled upwards through all 3 layers and the top one is drilled sideways and hidden once the glass is fitted