A blanking plate is usually used to cover where an accessory once was, and do not have any connections on them. They are just a piece of plastic with 2 fixing screw holes drilled in it.
You should join the live and switched live cables (and neutral if there is one) with strip connectors, and join the earths in the earth terminal of the backbox. The connectors should all be housed within the back box of the old light switch, and then fit the blank plate to cover the front of the box.
Fitting an architrave box and blank plate is a good idea.
You should join the live and switched live cables (and neutral if there is one) with strip connectors, and join the earths in the earth terminal of the backbox. The connectors should all be housed within the back box of the old light switch, and then fit the blank plate to cover the front of the box.
Fitting an architrave box and blank plate is a good idea.