Much depends on design but there are a few wireless switches both wall mounted and like a TV remote. The unit would normally replace ceiling rose but there are also types that plug in between bulb holder and bulb.
However it may be impossible to fit in a neat way only you can work that out. MK make one type and B&Q use to stock the other type.
When I wired my wall lights I used a standard conduit box to terminate the cables so it could be replace with a socket type ceiling rose if required but my fathers house just has wires sticking out of the wall which always seemed a bit of a cowboy job but 1954 when they moved in materials were in short supply. To add to their system would be hard but mine easy.
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