I'd probably keep the 7800X3d. It's pretty much the best gaming cpu at the mo and uses a lot less power than it's immediate competitors. Also the AM5 platform from last bit I saw will be supported into 2025, (and maybe 2026), so you have a good upgrade path of just switching out cpu in future without getting a new mootherboard.
As you're looking at 1440p gaming and was considering a 4090 at £1600, I'd go up a bit from 4070(which is compareable to a 3080 but more efficient), and go with either a 4070ti or 7900XT...they're fairly evenly matched, I think 4070ti techspot had the 4070ti 22% faster than the 4070 at 1440p over their game average. Main diff is 4070ti has better raytracing and dlss, 7900xt has more vram, so pick your poison
as for ram, I'd stick with 32gb of 6000C30 to 6000C36 area. I don't think the 7800x3d is that picky about having faster timing..just try and get amd expo, then at least it's been done by manufacturer to be used on amd motherboard, but not essential, as they're both really same thing (expo or intel xmp)...seen 326000c36 corsair rgb vengeance for £110, the 6000C30 for £140, or the dominator 6000c36 for £149 here(the 6000c30 variant was £220)
For gpu, I just chose those below or on msrp. no point spending £100 more for 1fps diff. I checked the gainsward on guru website and they gave it thumbs up...their is a palit also slightly cheaper but preorder only at mo
the bequiet psu slightly cheaper on OCuk, but again preorder
My basket at OcUK:
Total: £1,678.97 (includes delivery: £0.00)
anyway, hope this just gives you another idea, and doesn't comfuse you or anything..just another opinion
