I was wrong to be sceptical
I was sceptical despite the excellent Truspilot reviews. I bought the Windows 11 Home to Pro upgrade at considerably less than half the price asked in the ComputerActive Software store, which, desrvedly has dreadful reviews. At £19, it was £100 less than what Microsoft wanted. So my scepticism was justified. However, the instructions were good and the licence key worked. My fears were unwarranted: it went extremely smoothly. Thank you, TheUnitySoft. I wish you every success.