I would recommend using a good quality white sealant. apply masking tape around the socket leaving approx 2 mm gap on the socket and tiles. force sealant into the gap with mastic gun. use your finger and neatly smooth excess silicone off. remove tape, then very lightly with a wet finger or thumb, smooth again. should leave a very neat finish with the gaps filled in. other option is to use a oscillating multi tool with tile attachment. mark around socket with sharpie pen. remove socket, cut tiles with oscillating tool, then refit and sink sockets in and apply grout.