I have just been offered a month's work, so to compensate me for coming out of retirement I'm wondering about upgrading my camera. I've owned my Nikon D50 for a few years now, and get decent results with it. I'm a semi-serious amateur, and have long planned to do more photography in my retirement. Fairly obviously I'm looking to stay with Nikon to utilise my existing lenses, and I'm thinking a D-SLR is still the best choice - but which one? Budget will be around £500 - £600 for body only. Any recommendations?