Very Helpful vdo Guys <3 Nice Work <3

Probably a noob question! You said to disconnect the LAN cable. Do we have to even if the modem is switched off and relevant plugs are pulled from the socket?

Yes. Disconnect everything. Our ancient copper phone line network doesn't have surge suppressors, so it will carry a surge built up miles away. It might not even be raining in your area when you get hit with a surge.

Also with regard to the video, can you let us know how long can you use a branded power supply? I have been using my Antec PSU for bit over six years. It works fine still, but i bought a new Ryzen system recently, so just wondering whether that's okay for new components.

PSU's have quite a long lifetime, hence most high end models getting a 7 year warranty. 6 years is fine. You should be good for another year or two atleast. The only thing though, approximately drop 5% of your peak wattage per year of use and try not to load it beyond that. So treat your HCG520 as a ~400W power supply - which is still plenty for your system.