What XBox One do you have? There are some great deals on clearance stock of the original model but I would expect you do get plus £100 trade in regardless.
It's a difficult choice - there are a lot more exclusives on PS4 that you won't get to play on PC, but cross play between XB1 and PC means that you can slob back on the sofa rather than the PC if you want.
Both consoles support remote play to a PC as well, via their own apps.