Do you have a source for grid frequency taking into account leap seconds? I had a quick look around for information about the UK grid and can't find any timeke

Do you have a source for grid frequency taking into account leap seconds? I had a quick look around for information about the UK grid and can't find any timekeeping details. Also, wouldn't they have to slow down slightly rather than speed up? The second at midnight effectively takes twice as long, which is equivalent to the grid's waveform stopping for 1 second.