err, the op was asking about how to supply a garage from the household CU, iggifer said a 16A supply would be good. your method would be to supply it with 16A and then run the the lighting off the 16A radial socket circuit. "you say, how could a fault on the lights take out the sockets". well and earth fault would presuming there was an rcd in circuit, either at the supply end, not advised, or in the garage.
Yes I know what descrimination is!, that is why it would not be beyond the scope of let, say £30.00, to supply with a 20A fuse, non rcd ptrotected and then run to a garage CU and split the final circuits in 16A sockets and 6A lights.
descrimination and inconvienience in the event of a fault are 2 different thing, but can both me managed for £30 quid more.
why run lights of a socket radial in a remote location? when it can be done so easily, a lot better