I enjoy sketching but find that my pictures smudge a great deal and always end up looking a mess. I've tried a fixative but it has such a strong odour - is there any other method I can use to preserve my pictures?

You haven't mentioned what you are using to sketch. Assuming it is a very soft pencil, charcoal or Conte crayon, you would need to fix the sketch. Actually, instead of conventional fixatives some people sear by hairsprays, so you could try a few and see which smells best! Other ways round the problem are to use harder pencils and a spiral-bound sketchbook which won't rub laterally and therefore reduces smudges. Also, in recent years, Daler-Rowney have introduced their Perfix Colourless Low Odour Fixative, which is ozone friendly. This has hardly any smell whatsoever, and is well worth trying.