A quick update, Everything has had a coat of primer. I have fitted the supports along the top and bottom edges of the drawer sides, which can be seen in this picture.
IMG_1999 by
my0771, on Flickr
In order to get the maximum support I have cut some corner pieces which have been pocket holed in place.
IMG_2011 by
my0771, on Flickr
I have made some leg extensions which will be added next.
Still unsure about fitting the drawer runners, there will be a 30mm plinth along the top bottom of the sides. The total height it 580mm so the drawer fronts will be 520mm less kerf. This will leave around 490mm for the two drawer boxes.
If anyone can see any issues with this please let me know.