it's not too easy to give an exact answer. you need to know what resolution and framerate you're gonna be playing at. a 3070 Ti is probably a card that is aimed at 4K 30-60fps or 1440p 60-144fps.
if you're playing at 4K then the thing that holds you back the most is GPU power so your CPU isn't really that important. if you're playing at 1440p 144fps then you'll need good GPU power but also a fast CPU to keep up with all those frames.
if you only want to play at 4K 30-60fps then i'd recommend at a minimum: an Intel i7-8700, Intel i7-9700K, Intel i5-10400, or AMD Ryzen 5 3500. i pick these because they're 6 core CPUs with hyper threading or have 8 cores (with no HT). for gaming i wouldn't go below 6c/12t or 8c/8t. also you don't want to go below Intel 8th gen or AMD 3000 because Windows 11 support is patchy or non existant.
if you are playing at high refresh rates then i recommend at a minimum: intel i7-8700K, intel i9-9900K, intel i5-10600K, AMD Ryzen 5 5600X or AMD Ryzen 7 5800X. you want a fast 6-8 core CPU with HT and some overclocking potential.
the rest of your system isn't really a probably. RAM is RAM but you wouldn't want to go below 16GB at 3200MHz. 16GB is still fine today for gaming but if you can fit in 32GB then go for it. i think the highest speed you should get is something like 3600-3700MHz. you can go higher but there are diminishing returns. also, memory speeds are more important if you pick an AMD cpu. they like fast memory and there are more compatability issues so you need to be more picky when getting RAM for AMD.
as for SSD you can't go wrong as long as you make sure it's an NVME drive (slots into your motherboard instead of using a cable). ideally you'd want one with at least ~3GB/s. a PS5 can do 5.5GB/s for example but on PC you can go up to ~7.4GB/s. SSD speed will become more important in the next couple years so the faster you can get the better
PSU is quite easy. there are calculators out there that will tell you how much power you need once you've picked your parts. right now a 750W PSU is probably the most common. your GPU is the part the sucks the most power. if you have a really beefy system then 1000W. make sure it's a good brand. there a list of all the best brands out there (you can find it if you need it). EVGA or Seasonic is always a safe bet. Corsair are good too.
everything else is just preference really. get a case you like the look of (but make sure it's compatible with your motherboard/psu/cpu cooler/gpu). if your CPU doesn't come with a cooler you'll need to buy one (make sure it will fit in your case). buy a keyboard/mouse you think looks cool. get speakers and a display.
TL;DR i reckon you're looking at about £900 for a system with a 5600X, 16GB RAM, 1TB SSD, motherboard, case, CPU cooler, and PSU. NOT including monitor, keyboard/mouse, speakers, etc.