Dyson V6 sold out quickly when it was £199 with £20 off coupon a few weeks ago. It's now back at £189 with a similar £20 off of a purchase over £150 using Promo Code: TDX-GNKF (Offer Ends 04/09/16) making the cost £169.
Don't forget you can use your clubcard points to bring the price down further - plus you should get 169 points for the purchase. And you should get a small amount of cashback through Quidco/TCB.
Update: TCB offering 6% cashback boost on purchases until 1st September (more for Plus members, I think). Should be worth at least £8.95 if your tescodirect order tracks successfully.