Eugene's observations

Just 18 days remain before anyone wanting to upgrade to Windows 10 will have to spend £100 on a license.

Should you ?  Almost certainly yes.  The facts are that the interface is much the same if done properly so there's nothing to be scared of in that department.  The advantages are in the indefinate support, the enhanced security, and greater functionality (which is only apparent if you go looking for it).

Three things to remember though.  Always take a backup before any change - ideally an image of the entire disk.  Also check that printing and virus protection are intact after the upgrade: they are sometimes left in need of repair.

Make sure you leave several hours for an upgrade, perhaps two to six depending on the speed of computer and internet connection.

You can have your cake and eat it by upgrading to Windows 10 so that Microsoft records your activation.  Then use the image you took in step zero to restore the computer to the previous old version, like nothing happened.  Now when you are ready to move to Windows 10 you can just install it without any license cost as the key will have been recorded already and will be supplied by the central server.