Apple were previously replacing iPod Nano 1st Generation devices with 6th Generation due to the product recall, but it seems that now they are sending out 7th Gen devices (as per many various forum posters).
If you have one, it might be time to trade it in if you'd been holding onto it.
It should be replaced with the 16GB Nano 7th Gen worth £129 at retail price - although this isn't guaranteed, it is what most are getting.
Send these highly dangerous iPods in and do yourself a favour ;)
It seems to be luck of the draw, if you don't get a 7th Gen, then it will definitely be a 6th Gen.
Direct link to page will be posted in the comments.
YOU MAY NOT RECEIVE A 7TH GEN, MANY HAVE RECENTLY RECEIVED 6TH GENERATION NANO'S - YOU WILL RECEIVE A SUITABLE 'REPLACEMENT'.
real link for getting a replacement:http://www.apple.com/uk/support/ipodnano_replacement/
GOOD NEWS! If you do get a 7th Gen, you will also get a free 30pin to lightning adaptor worth £25!!