I missed the start of the programme and the credits didn't say what the piece was. The TV listings in the paper gave no details. This was pe-internet ubiquity so I was unable to find out more. I mentioned what I'd seen to a few friends for whom it rang no bells. Infuriatingly the all-female comedy sketch show 'Smack The Pony' appeared to parody the piece a while back but gave no hint as to what the source material was.
Now finally I've been able to identify the piece thanks to a review in the Guardian that seemed to describe exactly what I had seen. It turns out that the piece is called 'Rosas Danst Rosas' by a Belgian choreographer called Anne Teresa De Keersmaeker. It's apparently very well-known in the dance world and has recently revived (hence the Guardian review) with De Keersmaeker herself taking part.
Here's a youtube video of all or some of it (it doesn't make clear which) which is well worth watching, enjoy: