I would say wind & rain unless you know something i dont about welsh cats 'lol .....i guess you need some dry sunny weather then youll find your flower heads should point upwards by themselves.

I`d say the rain as well.

Yes, definitely the rain - it has happened to some of mine!

I would say its down to the weather, a little tip for you here, in future years before growth really gets going, put a few sticks in the ground and criss cross a few of the sticks so that the foliage and flower stems grow through the holes created position this aprox just over a foot from the ground, this will stop the flopping and the framework will be hidden in all the foliage, another tip for you is that once all the foliage and flowers are over and looking rather sad then cut all this away to ground level, keep watered and before long new lush foliage will be sent up and you may get a second flush of flowers.

Thanks Julien. That sounds like a good tip. I've tried staking them after they fell over but the stems have gone hard and twisted into shape. yes the buds are pointing up again after today's sun, but sadly the long stems are still more or less horizontal.

About the framework - would the criss-crossed sticks be all in the same plane? so its a bit like a trellis?

Thanks to all for your answers. It seemed like it was too much damage just from rain!! ... the power of water I guess!