Hi Dave
Moving the ONT is actually easier than moving an old style master socket as all the connection are simple plug and socket.
Unless you plan on hitting it with a hammer there is no risk of damaging it.
Unplug it from the mains, unplug the fibre connector...make sure you have a cap to cover the end of the fibre plug.
Lift it off the screw heads that are holding it to the wall.
Edinglas
Now how do you extend the fibre connection to the new position of the ONT?
Use an SC/APC coupler and single mode simplex OS2 fibre cable of required length with SC/APC plugs at each end.
You can buy these separately or in a kit
I found the following guide and kit to doing it. Seems pretty simple enough.
https://www.premitel.uk/consultancy/expert-advice/how-to-move-the-fttp-ont/