Agreed, £40 is standard at the moment but I thought it worth mentioning as its a substantial perk. The Essenza is a different (and cheaper) model without an aerocinno so not really comparable.
All Nespresso machines, regardless of where you buy them from, come with a £40 nespresso voucher to spend on coffee pods & Accessories. It is a Nespresso promo rather than a Debenhams promo. Not an amazing price either, I got my Nespresso Essenza at the start of Jan for £79.99