It's not, green sources cost more, so you have to pay more, fairly simple really.
They don’t, wind power is THE cheapest form of new generation and that gap is getting wider all the time.
Bills are going up because a significant amount of our electricity still comes from gas fired stations and the price of gas is creeping up all the time (I know it has dipped at times but generally speaking).
The actual energy cost is only a proportion of your bill. The other reasons are that initiatives like smart meters, green deals, support for those on benefits and deals the government has made to get infrastructure built (Hinckley point C) with a guaranteed energy price above the market rate comes off your bill too. Distribution and management of the grid costs are only going to go up.