After putting the display on a timer interrupt as well, I've managed ti get the whole thing going. So now the whole thing is interrupt driven. I optimised the IRQ routine so that the delay between each packet has been reduced and the overall update increased to around 20ms (rather than 100). So I've now started to wire up the prototype I started a while back but it'll take a while.
I put a new nib on my soldering Iron, but its already starting to lose its heat conductivity. Im not sure why but I think I may have it too hot and its losing its "tip", but I dont really know - this is the 1st time I've used an iron this long!