Hi Izzyb I am thinking on a macro as well. I'm looking at 3 at the moment a tokina 100mm asigma 105mm and a tamron 90. They are all under £400. Dont think they auto focus but you dont want auto focus on macro anyway. There is also a sigma 150mm costs about £580 that looks good. good luck graham.
Hi Izzy. I bought the Sigma 70mm f2.8 macro lens which is superb, But I now wish I had gone for the 105mm or even bigger. Many macro subjects disappear if you get too close, so the extra distance between you and your subject is best served by a longer focal length lens like the 105mm.
Sigma 105mm EX DG macro as my first dedicated macro lens, it was awful in every way, not very sharp and sluggush.
Tamron 90mm f2.8 DI SP. I enjoyed that lens and it was pin sharp and good contrast.
Nikon 105mm AF-S VRII f2.8. A truly great lens, sharpest by far, good contrast, good bokeh, a little heavy compared to the other two. VR is good if you use it as a general purpose lens as well as macro. AF-S is quick and precise but as others have mentioned it is necessary for macro work.
The Sigma 150mm macro gets good praise but I have not tested it; it would give you more working distance which is good for insects but not necessary for flowers.