How much wind power is there roughly in Britain and its surrounding?
2.2TWe on average in the seas...
The uk uses less than 350 Gigawatts every year, so the sea can provide about 6 times the current UK energy consumption:
80 GW in shallow waters (0-25 m)
270 GW in seas of depth 25-50m
(up to there is sufficient to meet all of the UK's 2016 energy consumption)... There is also:
790GW in seas of 50-100m
1030GW at 100m-700m
https://claverton-energy.com/two-terawatts-average-power-output-the-uk-offshore-wind-resource.html
https://www.statista.com/statistics/323381/total-demand-for-electricity-in-the-united-kingdom-uk/
For onshore resources, you can add another 100GWh.