Currys have 25% Dyson products when you trade in *any* old vacuum cleaner.
"As part of this great promotion you can save 25% on any Dyson vacuum cleaner, all you need to do is bring in your old vacuum cleaner to your local Currys store; plus well even recycle your old one for free! This limited offer extends across our whole range of Dyson vacuum cleaners including Dyson uprights, cylinders and handhelds"
As an example the Dyson DC31 Animal is on their site for £159.99 which is not the cheapest....but trade in an old vacuum cleaner and it's £119.95. Go via topcashback and you may get another 3.5% cashback too.
Should I need a new Dyson I'd be tempted to go in with a USB powered vacuum cleaner from poundland....but you could, as my mate did today, salvage any old vac from your local tip / recycling centre for a few quid.