External Hard Drive on a Wireless Network

[#1]

I have a PlusNet ThomsonTG585 V7 wireless router. I use a laptop, via a wireless connection to the router.  I would now like an external hard drive as a data back-up.  It would have wanted this hard drive accessible through the network, but most seem to be USB and cannot be plugged directly into the router.  So I would need to plug it directly into a USB socket on the laptop whenever I wanted to do a back up?
I appreciate that if I set up my old desktop, I could use that as a link for the external hard drive, but I don't really want to do that. 
So is there a work-around or a type of external hard drive that can be used on a stand-alone basis in a network?
 

[#2]

Yes, lots of options for NAS storage solutions (Network Attached Storage). This is a stand-a-lone box connected to the network (I recommend wired not wireless).
A few examples here at Amazon or just google for NAS. Anything from £100 upwards.
Buffalo are recommended.
For security I would recommend going for 2 drives in a raid 1 (mirrored) set-up. It adds to the cost but if this is for backups / storing important info it will ensure you won't lose any data should a drive fail. Note: not all enclosures include disks so read the descriptions carefully!

[#3]

I got one on ebay which was basically a single 750MB SATA drive with a board on top which allows connection via USB or Ethernet.
Supports connection via http, ftp, nfs, Windows share scheme thing.
I have it cabled into a router and use wireless with rsync for backups - the wireless makes it slow, but I don't have to cart it around with for USB connection.