Thanks Alan and Tony for your replies.
The wall has gone up today to about 3ft. high with commons at the rear. Whilst this wall appears quite sturdy, I would have thought that the addition of any stone/ sand/ cement behind it would have been the main strength of the wall. It has a good amount of re-enforcement bar behind the wall and weep holes are in place.
I plan to chuck the MOT with a mix of 6:1 cement behind the wall and am surprised you think this is wrong.
I will use 20mm stone next delivery as you suggest, but the MOT was specified by a professional structural engineer.
I am told the MOT is normally this colour and is probably recycled. I was expecting 40mm to dust stone of a limestone appearance.
The weep holes also seem irrelevant as the ground is very porous and would drain past the back of the wall foundation rather than build up behind the wall.
Many thanks for your thoughts and suggestions, they are very helpful to a newbie wall builder.
Come and have a look Tony, I'm only 6 miles from Leigh!
Great site many many thanks,