Hi simon that was exactly the issue, i was using build:
"CatalystPM 4.30_m283UB_HD"
Which wouldn't allow me to resize the window even though my screen rez was big enough. Just got home yesterday and malled out with version:
"CatalystPM 4.40_m327_HD"
Which worked a treat.

Thanks everyone for the help, i thought i was going a little mad!
Best

Andy