They're a bit hit and miss in my experience, Carl; some years I get enough saffron for a few good meals, and then I'll get several years without any of them flowering at all.

Saffron crocus grows very easily - but it doesn't flower easily.

A few things worth trying ...

Use very deep pots, the deepest you've got. Saffron bulbs like to be planted deep. Don't let the bulbs become crowded; they're fussy about that, too. Make sure you've got really good drainage in the compost - they're even fussier about that.

Some say it's worth putting the pots into the (unheated) greenhouse during the winter, after flowering (or if they don't flower), to help bulk up the bulb for next year. Flowers come from big bulbs, not small ones. Certainly water and feed while the plants are green.

When they do flower (any time from Oct to Dec, I find), the bit you're after is the stigma; long, red, floppy things sticking out of the bloom. Pinch them off as soon as they appear - first thing in the morning, preferably - using tweezers. The stigma are joined together at the base - take them as one unit. Put that on a bit of loo paper, folded over to stop the "red gold" from blowing away, and put it somewhere moderately warm (kitchen, perhaps), for a day or three, until it is completely dry - really dry and papery to the touch. Then keep it in a jar with a good lid, in the dark.

Saffron potato salad on Boxing Day ... now that really does impress the non-gardeners!

And - to any passing browser - please remember only to use saffron crocus for cooking ... if you eat any part of the Autumn Crocus you will die. Which will probably get you into trouble at work.