OK, since nobody replied I bit the bullet and have upgraded to Windows 10 on my HDD.
So far so good.
However, I tried to migrate to my new Samsung 850 Evo but got an error message: 205500 (0322BC): Failure to read source disk or something.
I ran check disk and tried again with the same result.
The weird thing is, when using Samsung Migration tool, the source disk is also titled 850 EVO SSD however with the correct size of 1TB.
Help.