Thanks Mousie!
Looking at it again, I'm thinking if I spit it vertiacally into three - strips of 2 blocks - 3 blocks - 2 blocks, then SITD only down either side of the centre strip/three patches of each block, then I won't have to worry about the joins. So now my only question is this - when I SITD the horizontal lines, how much fabric do I need to leave at the points where I'll be joining the sections? Does the 1/4" of the seam allowance give me enough room to manoevre? I've only ever QAYG by hand and then I left tails of the quilting thread hanging and finished off after I'd joined the sections. Obviously I can't do this by machine.