Nikkor and Nikon are one and the same. Somebody else might fill in the details but it seems to me that Nikon brand all of their lenses as Nikkor. No idea why!
You need to be a little careful as your camera doesn't have a built in auto focus motor so whatever lens you buy will need a built in auto focus motor. In terms of Nikon's own lenses, that means that you need to look at AF-S lenses only.
If £100 is more the sort of budget you're working with, my two suggestions would be these, but both will need to be bought used to fit in budget.
Option 1) Nikon (or Nikkor!) 55-200mm AF-S VR
http://www.jessops.com/online.store/products/50317/show.html
Option 2) Tamron 70-300mm DI LD
http://www.jessops.com/online.store/products/66332/show.html
The first is probably the better lens in terms of image quality but the Tamron is 33% longer so potentially more useful particularly with smaller animals.
If you can stretch the budget, the two that I mentioned earlier come with no such drawbacks.
They're these two. I guess both are around £250 used these days though the Tamron is quite new and maybe hard to find.
http://www.jessops.com/online.store/products/35945/show.html
http://www.jessops.com/online.store/products/77949/show.html
Edited to add: Ha ha, beaten to it!