Intermittency is just not a real problem for the sector. Wind levels are consistently high enough to power turbines over 90% of the time, and when the wind isn't blowing in one part of the country it is elsewhere. But even if we did experience a wind drought, that's why Miliband & co are increasing the number of gas powerstations and bringing on the 2 nuclear reactors.
The bigger problem is that we generate too much power with wind and don't have the capacity to take it, but that's being addressed by the deal they made last month to connect our windfarms to EU ones, so when we have extra capacity we sell it to them and vice versa.