Finally done as I had a slight delay with a replacement cooler.
https://i.imgur.com/y6z9ISC.jpg
I've done some small upgrades on PCs but never built one. so this was a bit of a learning curve. Thought I had knackered it at one point as I was struggling to get the USB plug from the case onto the motherboard because I'd stuck two fans in the way, and I bent a pin. after sitting and looking at it for several days crying, I managed to gently straighten it and got the plug on. The hardest part for me was small plugs going onto the motherboard when it was inside the case. The videos made it look like a doddle but I had to fight every one, especially those little single front power reset things. I connected all the fans to the hub in the end as I found out they took 3 pin as well.
I turned it on and the monitor was black, after I had announced to the wife 'watch me enter the bios now and set it up' - she gave me a little smile to try and mask her disappointment and boredom. Turns out I had put the port display into the motherboard and not the GPU. Fixed it and the bios came up after a reset. I was fairly happy!
Windows went on fine and I've checked as much as I can think of like USBs, reset, power, RGB controllers etc all work so far with no crashes, resets or smoke. Cable management can wait, I don't want to ruin it, plus I'm moving into a bigger room and I'll take some pictures when it's set up.
I'm very happy with the PC, it's ridiculously fast compared to what I'm used to. Win 10 boots in a few seconds rather than 10 minutes. The little m.2 drives both work fine and fast. The only thing I was disappointed with was transferring files to a USB stick, but I presume that's the stick's fault and not the PC. M.2 to M.2, even 6GB films were instant.
Thanks again.