Just to follow up on this guys - spoke to the people I bought it from, they fobbed me off with "speak to nintendo", so, I set it up in my room before I rang them and it worked fine...! So set it up in the lounge (the room in the pics) and it also worked fine! so I have no idea what was going on there - perhaps it felt unloved, but its fine now! Set it up EXACTLY the same as before too, how strange! Christmas tree and all christmas cards etc gone now, although the christmas tree was never switched on when I was trying it... oh well!
Thanks for all your help guys