Update on the IRQ problem:
Still haven't managed to set the address pointer to the correct register using wire but 1 major issue is solved.
The Control register address words are not contiguous...they read from 0x00 to 0x0B skip 2 then start at 0x0E again. so reading 14 bytes does not read all the registers as in my code but only reads as far as the 2 unused registers 0x0C & 0x0D. This means the IRQ status is never read and hence the IRQ pin is never cleared!
Oh well...I'm always telling people to RTF datasheets...... 
At least now I can get on with the 24 x 22 matrix when the parts arrive from China. 