i had a refund myself due to some loser selling me a 360 a few months back, then after the sale he said use western union to pay him in turkey. i emailed him telling him to shove it.
anyway to the point, the refund in paypal took over a week if i remember correctly, and then thers another week(ish) to transfer the money from paypal back to your bank.
All in all took a fair few weeks to get my money back, although I canceled my payment (which like yours was paid on a debit card) rather than him paying me back although my situation was quite similar to yours. I paid via paypal for the 360 then he started being arsey about it saying he wanted WU (turned out he had hijacked someones account). hope this helps