I bought the 13" base model last Monday. I like it so much I'm wishing I'd gone for the next model up, the 2.4/8GB/256GB. As I'm still within the 14 day period would I be able to take it back tomorrow and just pay the extra £150 to get the next model up? Or would they have to refund the original purchase and I just buy it? Should I format before taking it back or anything? Going to phone the store this afternoon and ask but just wanted to see if anyone here knew? I'm in the UK if that makes any difference.