How Many Wind Turbines Would You Need To Power The Whole Of The UK?

You couldn't do it, because wind turbines only produce electricity when the wind is blowing, and sometimes it isn't.  There has to be other energy generators, too, if we want a reliable electricity supply.  

Moreover, they only produce electricity.  We could all drive electric cars and use electric stoves and boilers instead of gas- or oil-fired (or even solid fuel like wood and coal.  But assuming that the question is only thinking to replace the current electricity supply, not to convert everything else to using electricity as power source, too:

The average very large wind turbine produces 500 kW, at any one time.  Total capacity may be four times that, but 500 kW hours is about average.

UK electricity consumption is going up steadily, let's assume we need 420,000 GWh (per year, in the near future) following 1998-2004 figures from the Electricity Producer's Association.  This suggests hourly averages of 48,000 MWh demand.

To entirely meet average demand, if the wind were blowing then, we'd need about 100,000 large wind turbines. That would never be acceptable to most of the public.