On the wildlife lens front, I’d probably go as above - the Sigma 150-500mm seems quite well-regarded, and would likely fit into the budget without persuasive use of a shoehorn. If you were looking a step up, in both quality and price, there’s no question the Nikkor 300mm f/4D AF-S is fantastically sharp, but you probably won’t find the AF-S version for less than £600 used. (There is also
its predecessor, which apparently is slower in focusing, but similarly high quality optics; I recall that’s occasionally available much cheaper)
As for other lenses: you might consider a Sigma 10-20mm f/4-5.6. The field of view is quite astounding, and it’ll focus fairly close up, making for new compositional possibilities, whether you’re shooting an excellent beer in a cozy pub, or a stunning vista beneath a glowing sky. And then there’s the previous (ie much cheaper!) version of the Sigma 30mm f/1.4 - admittedly rather soft wide open, but still, f/1.4! Again, that wide aperture starts making new possibilities available, with such thin DoF. Each are, as I recall, somewhere around the £200-240 mark, used.
Another option, if you’re at all interested in macro photography, is a set of extension tubes. What the new minimum focus distance will be depends on the lens’s internal design, but it’ll be short.
Admittedly, it does feel a bit odd wielding a Sigma 120-300mm f/2.8 with the front element about an inch from the subject.. more portable is the 30mm, which I used with the 6mm tube for this photo of
frost on a leaf, a couple weeks back.
For the body, probably a D90 -
MPB, for example, is showing D90s for around £280, versus D7000s for around £440. A D90 plus a 150-500mm would fit, or both the above.
