There's no wind generation that costs 5p/kWh. In fact there are several CfD-subsidised units getting over 22p/kWh, for example Burbo Bank Ext, Dudgeon and Walney Extension. Many ROC-subsidised units getting even more than that. That's before backup, grid balancing and expansion costs.
2/ Britain still prices almost all electricity at the marginal cost of gas, even when most of it comes from cheap wind or solar.
Wind generation: ~5p/kWh
What you actually pay: 25p/kWh
That massive gap is baked into the system.