Tidal energy doesn't compete with wind, it competes with energy storage. Having virtually no wind production over the whole UK for a week happens regularly; in fact this last week is a good example - production has averaged well under 2GW according to https://www.gridwatch.templar.co.uk/
On a windy week production can average over 10GW, but as yet grid scale storage is about as immature a technology as tidal generation (with the exception of pumped hydro, and there is a limited number of suitable sites for that).
