Hi, thanks @BuZz - all seems to work now. I got a few errors flash past as it was building but nothing that has stopped it from working. Hope it fixes it for you too @simonster.

I did have to play about with the retroarch.cfg file in the /nes folder to get it to work with my NES controller, but fixed it by setting the player 1 control to:
b_btn = "1"
select_btn = "2"
start_btn = "3"
up_axis = "-1"
down_axis = "+1"
left_axis = "-0"
right_axis = "+0"
a_btn = "0"

All the rest to "nul". If I didn't do this then as soon as I started a nes game it would not respond - I'm sure there is a proper config, but I spent a few hours playing about with the config files before I got it working so now enjoying some sweet retro gaming :)