Ok, I tried again with the hdmi cable unplugged, just the same. If I leave the stick in when it reboots, it says 'starting', but when it boots without a stick in, I get the VU+ screen.
I've tried 2 different 1G sticks and a 4G one. Is it worth buying another? The box seems to detect and read the sticks ok.
I'll message the guy I bought it from tomorrow, see what he has to say.
Thanks again Maxwell