So a $10Bn pound investment produced 243 GWh of power over a 25 year period, or nearly 10GWh per year. Perhaps you had better do the math.
The costing is a lie anyway, like everything coming from the gangreen. It did not include the interconnexion cost (which is astronomical for any offshore installation), not the maintenance cost, not the intermittancy cost, not the distmantling cost...
I recall that during the California black-out crisis under Grey Davis, 1 MWh of electricity was going for about $109.
243 GWh is 243,000 MWh, multiply by $109, we get $26.5 million, convert into pounds is something like ₤10 mil.
So it cost ₤10Bn to generate a total of ₤10 mil worth of electricity.