Have a look at the Nikon AIS lenses, which are the older lenses before the digital age. They are all full frame and give great results. Also, consider the Nikon 70-300mm F4.5-5.6 VR which is very sharp throughout it's range. If you can find a secondhand Nikon 70-200mm F2.8 VR for less than a £1,000 grab it. It can be used with either a 1.4, 1.7 or 2x Nikon converter. I've used mine with both the 1.4 and 2x converter so, giving me a F4 98-280mm with the 1.4 or a F5.6 140-400mm with the 2x converter. I've posted a link to Ken Rockwell's site which give information on all Nikon lenses.
http://www.kenrockwell.com/nikon/nikkor.htm