I would go for the iPod Touch 4th gen in black.
If you can afford it go for the 64GB version.
I currently have an iPod Touch 32GB 2nd gen which my mum gave to me when she got an iPad 1 but I am think about upgrading my iPod Touch and buying an iPod Touch 64GB 4th gen.
If you do buy an ipod Touch then remember that it will only have Wi-Fi for downloading apps, music from iTunes store and surfing the web.
But as more and more places have free Internet access then it is not so much of a problem well not for me anyway. And you will most probably have Wi- Fi at your house like I do.
If you go for an iPad 2 or a seconed hand iPad 1 then you will get a bigger screen as well as Wi-Fi and 3G but you to use 3G you will need to get a mobile sim card and sign up for a monthly mobile data contract which could get expensive. But have a look at Tesco Mobile for a mobile data contract.
http://phone-shop.tesco.com/tesco-mobile/sims/
Also the iPad is not as portable as the iPod Touch.
My mum loves here iPad 1 and thinks that it is exellent but I would presonally go for for the iPod Touch 64GB 4th gen in black.
Here is a link to a thread that I started yeterday were I have posted 2 links to the cheapest prices that I could find for the iPod Touch 64 GB 4th gen and a link to the offical Apple UK page for the iPod Touch 4th gen.
http://forums.digitalspy.co.uk/showthread.php?t=1549846
I hope that I have been able to help and good luck choosing the right Apple product for you.