Another method that I learnt from a housemate when I was a student - laundry washing powder, especially the super-stain-removing stuff. Use it like bicarb, but allow it to sit/soak for a while (if you can pull apart the oven and soak in a laundry sink, leave it over night - good for crusty baking trays). It works!
Obviously a little more difficult if it's on the sides/top of the oven, but just scrub it with a laundry powder/warm water mix.
Does the smell affect other food you cook in it?