I also have 15 sprout plants
you can order them online as collections e.g. D.T.Brown will do a cauliflower collection or autumn brassicas etc. so you might get 5 cauli, 5 sprout, 5 cabbage etc. but you order them months before they send them which is what can cause the confusion.
Had good success in the past though, ordering the autumn ones and filling all the gaps in the allotment that have opened up and then having brassicas right through from November to May.
My ideal collection would be 5 cauli, 5 kale, 1 broccoli, 5 sprouts (no cabbage - doesn't do well on my lot) but sadly that is not a combo you get.
I generally give about half away to keep thing under control.
I am wondering if i can zigzag these in amongst the caulis that are already in on the grounds that those will be ready first but i am not sure they are far enough ahead.
I love cauliflower but you can have too much of a good thing as I discovered last year with peas.
And i never put in more than 2 broccoli plants now as they take up so much space!