I have done some picking apart and adding in, and I think the whole thing is looking better now.
I remade a few blocks using a new fabric - the one in the centre block above. It picks up the blue and the green and is just generally quite lively.
I then added a block of small blocks down the left hand side and put some strips of the low volume fabric in amongst the blocks to break them up. Unfortunately no picture of the whole thing yet, it's blowing a gale here today!