Here's the current listing at Microsoft UK then:
The links you need are here for the Lumia 950 XL in black. And here for the 950 XL in white. The regular price has been £339 for ages, which itself was terrific value. The Display Dock is sent to you after purchase, i.e. separately - the status of whether you also get a year of free Office 365 is unclear, but the Dock itself saves well over £50.
The 950 XL (and 950) still has just about the best camera in any phone in the world (in my tests on AAWP), a large screen to die for and is unusually flexible, in terms of battery, charging, storage and more. And will be well placed to run Redstone 2 and 3 next year.
What are you waiting for?
By the way, the Lumia 950 is showing at £249, still cheaper than I've seen it but not showing as an offer price for this weekend. And, crucially for me, also showing as 'Out of stock'. Implying that Microsoft seems to have run out of them, at least in the UK. Maybe this weekend's deal on the Lumia 950 XL will see stocks of that too finally run out, at least at Microsoft HQ?