More as a matter of interest I came across the CAA's 2013 stats for UK airports. Interesting reading. For international passengers the total number was 189.7 million. Out of that EU countries were 120.8 million. The top 7 were as follows
1 Spain 32.7 million
2 USA 17.4 million
3 Germany 12.2 million
4 Italy 11 million
5 France 10.4 million
6 Ireland 9.6 million (note Belfast is UK domestic)
7 Netherlands 8.1 million
Other interesting stats is that in April 2014 LHR had 6.1 million transit passengers, LGW had 3.1 million. UK total for that month was 19.6 million. I was never aware just how important transit passengers were to the UK.
The busiest international route in 2013 was LHR-JFK with 3 million passengers.