advice on fennel bulbs

Were the seeds labelled 'Florence Fennel'? You may have its close relative the herb fennel rather than the more dwarf Florence fennel cultivated for bulbs, especially if it grew tall. You can use the seeds for herb tea/cooking if you like, and the flower heads attract hoverflies if you're into wildlife gardening at all.

Hi HFB,
I had the same problem as you, so later (sadly too late for this year's growing season) I bought Florence Fennel seeds, variety forgotten, and I have actually planted a few just out of interest in little pots. Maybe will enjoy them in a micro-salad!
We can both try again next year... Luckily the more common - I mean in GB gardens - fennel is also an attractive plant, though I cut ours back drastically when it got too tall. It still has nice flowers/seedheads.