No. (Well not officially anyway).
Theoretically you have to pay for Windows 10 but, as long as the hardware on your machine is up to it, you can still upgrade from Windows 7 or 8 for free:
The first step is to ensure that your current version of Windows (7 or 8) has all of the latest updates installed.
Then you need to ensure that you know which version of Windows 7 (or 8) you're currently using. (i.e. 'Home', Pro' or whatever).
Next you need to install and run a program which will find the product key for your existing installation. (Belarc Advisor, which is a freebie, can do the job for you).
Then you need to follow Microsoft's upgrade procedure to get the same version of Windows (e.g. 'Home') as you're currently running. When you're asked for a product key, simply enter the one you've already got for Windows 7 (or 8).
However, given that you've acknowledged you're not technically-minded, Henry, I wouldn't recommend trying it on your own, as there are some potential problems that you might encounter along the way. It would probably make more sense to seek the services of a professional. (Alternatively, given that you can buy a refurbished Windows 10 machine, from a reputable source, for under a hundred quid, it might be time to change your computer).