1000 quid for that used PC is fair price since brand new parts cost double of that:
Eh, the system is likely a fine option for the money, but I wouldn't say it would be worth paying double that amount for new components with that level of performance at this point.
Keep in mind that the GTX 1080 is from the previous-generation of graphics cards and isn't being manufactured anymore, so its prices when buying new are no longer all that attractive. One could spend half as much as that graphics card (around £300 less) for an RTX 2060 or RX 5700 that would perform similar.
And for a gaming system, it would probably be better to put more of the budget toward the graphics hardware than toward such a high-end CPU and cooler, as CPU performance will tend to have significantly less of an impact on gaming performance in most titles. Spending £600 on a CPU and cooler while only spending an equivalent of £300 on a graphics card seems a bit unbalanced as far as allotting the budget of a new system would go. If one were building a new system, they could probably get away with spending around £200-£300 less on a CPU and cooler without noticing much effect on gaming performance.
I would also condense that £215 worth of SSD and HDD storage totaling 1.5TB into a single 2TB SSD like an Intel 660p for a bit less, while getting better storage performance, since all games would then be on SSD storage. Or another option would be to get a single 500GB SSD and a 2TB 7200RPM HDD for more storage with similar overall performance for close to £100 less. It would be possible to find better value options for some of the other components as well.
Again, that's not to say the hardware is a bad deal for £1000, and it's probably rather good for that amount, but if one were buying new components to build a system on their own, they could get pretty similar performance out of components totaling only a few hundred more, rather than double the amount.