I think Wayne may be referring to my recent request for help. I know it may be tedious for those who are familiar with all this stuff, but for a Newbie who is geriatric, we need all the help we can get.
The problem is really with the lack of info provided by the manufacturers. In my case, the manual for the Eachine 250 stated that the FC was CC3D. Since nothing seemed to work I posted a photo of the FC. After posting a photo of the FC here, I found that it was a F3 Acro 6DOF STM32F303. Now try finding that in a drop down menu.
That then led to another suggestion that it would be best to flash Betaflight. Another can of worms was opened.
I will probably now wait until I return home form holidays and contact a local FPV club and get some help there.
In the meantime I shall persist with the Youtube guides and forums even though it may be driving people to distraction.
Thanks for all the help so far anyway. And Wayne, I will try and find your other posts on this and see if that helps.