Hi Ian,
I can whole heartedly recommend Davinci Resolve as a state of the art editing tool:
1. The standard version is completely free of charge and seems to have nearly all the features of the paid for 'studio' version.
2. You don't even need to have a powerful PC to run it since when you want to work on 4K files you can click an option to generate @optimised' low resolution copies of your video files which are then used for all the editing work. The original high resolution files are still used by Resolve to render the output file. Of course a specialist PC aimed at video editing or gaming that has a high end graphics card will give users an overall more enjoyable experience.
3. YouTube is awash with lots of brilliant Resolve training videos that range for quick start guides through to studio level techniques. So getting going with Resolve is relatively painless and then gradually over a period users can learn new and more advanced techniques at their own pace.
All the best, Martin