This page on Wikipedia says that there are a couple of types of solar cells. One of them turns the light directly into electricity- photovolatic cells - the efficiency of those was low but has improved greatly. The other sort heats water inside the cell and the hot water generates the electricity from there.
https://en.wikipedia.org/wiki/Solar_cell
Possibly the most efficient use of solar heating is to not use electricity at all, and to use the sun to heat up something (water, pellets of glass or metal) and the heat is retained by the substance and is released over hours when the sun has gone down. I suspect that kind of thing isn't a lot of use in the winter in the UK but can be great in summer.