Usual reason for Sprouts to 'blow' this way is that the plants were not firm enough in the soil. Big argument about it amongst growers as to what is meant by 'firm' soil. Some advocate really stamping down the soil when planting, others say that merely staking the plants so that the wind cannot move it about is enough. One thing to be sure is that you should not plant Sprouts in recently turned over soil, say after potatoes have been lifted. (Unless you are on very heavy clay that is).
So takes your pick.
Now the good news is that even though your Sprouts have blown they are still very edible, just treat them like mini-cabbages. Stir fried with a little bacon mmmmmmmmm.

We sowed and planted far too many brussels last year and are overloaded with them - none of the neighbours will accept them as a gift, not even wrapped in a £5 note!
Interestingly, most have formed good, firm sprouts but some have blown! All were treated in exactly the same way.

Bulba - I'll take the spare £5 note off your hands :-)

Keep the money, just send us the sprouts. Ours have been destroyed by the extreme cold we have had the last week or so.

Thanks for all the helpful comments. Sounds like I did just about everything wrong. I planted some sprouts in the bed I'd just taken my tatties out of, and the rest in the bed that had just finished giving me a lovely crop of broccoli ... also, I didn't stamp them down or stake them :( :( At least I'll know for next time.

But I *do* like the sound of my mini-sprout-cabbages sharing a stir-fry pan with a tasty rasher or 2 of bacon ;)

Just sent OH up the garden with a spade, snowshoes, a torch and a Union Jack to pick sprouts, and after 10 minutes of searching around he found them. Hooray! Stir fried sprouts are one of our favourites. Next year we'll send a request instead to you, Bulba.
We didn't stamp down the soil round ours particularly hard, but we did stake them, and have had a lovely crop of beautiful, firm sprouts. I think the variety you plant also has some bearing on this. For the first time we've planted "Bosworth", and they have been wonderful in every respect.

I'll make a note in my diary - Bosworth it is for next year! Thanks for all the helpful advice ;)