I have disconnected a small wall light in my bedroom. I have insulated the three wires, blue, brown and earth. Can I now just cover it over with a plastic cover. I read something about disconnecting from the circuit and I don´t understand that!

Are these wires in a junction box? If so you can insulate the wires, as you have done and put a coer over them. If not in a box, you will need to remove the wires if possible, but you will DEFINETELY have to disconnect them in the panel and tape them off so they won't be used accidentally by anyone.

No, these are just sticking out of the wall. I cannot see how I could remove the wires. Sorry to be so stupid but I am an elderly widow and am trying to save money. I live in Spain so I wouldn´t think the wiring is the same as in the U:K:!!
Could I just put a box over them now that I have insulated them.

Missouri Bounds... many thanks I have done it. I am so excited because it all works properly. Thanks for giving up your time...

You are welcome. Glad to be of assistance.