Aha - on the back of adding value to the Lumia 640 and 640 XL, Microsoft has done the same for the 950 and 950 Xl by including a year's free Office 365 Personal with every handset (and the attendant 1TB free OneDrive space, importantly). It's all claimed via the Lumia Offers application, though do note some possible complications (via Andy Hagon, friend of the site).

From the blog post:

The Lumia 950 and Lumia 950 XL are the most powerful phones we’ve ever created, designed to work like your PC with innovative features such as Continuum and Cortana. To help you be even more productive, for a limited time in select markets, you can fully realize the power of Windows 10 with a 1-year subscription to Office 365 Personal included (MSRP: $69.99 USD) with purchase of a new Lumia 950 or Lumia 950 XL.

In addition to getting the most from your phone, the subscription also includes access to the latest Office apps on an additional PC/Mac and tablet so you can create, edit and save all your documents with ease across devices. With favorite Office apps including Word, Excel and PowerPoint, and access to 1 TB of OneDrive cloud storage, the Lumia 950 and Lumia 950 XL are the most productive Windows-based smartphones on the planet. Windows 10 scales apps for your mobile screen and bigger screen with Continuum and the Microsoft Display Dock accessory, giving you a consistent experience however you work.

Here’s how it works – Open the Lumia Offers app on your qualifying Lumia 950 or Lumia 950 XL or download it from the Windows Store. Choose ‘1-year Office 365’ from the ‘available offers’ list. Enter your email and tap ‘continue’ for instructions to claim your subscription. 

Importantly, this offer isn't global, it's only valid in the U.S., UK, Germany, France, Denmark, Finland, Norway and Sweden. Still, very handy for someone who's picking up a handset anyway. And I'd argue that the OneDrive 1TB bump for a year is worth £50 or so, effectively taking that off the cost of the phone?