Why don't British students go and study in other countries?

In the world of internationalisation and the increase in mobility in all areas of life - but especially in the number of international students coming to the UK - it is very interesting how few British students go abroad to study.
The Erasmus Programme is an exchange programme that was initiated by the European Commission 25 years ago, in a time that the commission didn't even have a mandate on education. The community only had 11 members and the Iron Curtain was still present. Humble beginnings aside, 25 years on, the programme continues to have a great impact on the development of Europe and its higher education.
In 1987, 3,244 students spent part of their studies in another member country. Three million students have followed their example in the past 25 years and the number of countries has grown from 11 to 33, including non-EU members such as Croatia, Iceland, Liechtenstein, Norway, Turkey and Switzerland. The budget of the programme for the period 2007-2013 is €3.1bn.
These facts, taken from the following article http://www.guardian.co.uk/higher-education-network/blog/2012/may/21/erasmus-programme-and-student-mobility looks at the impact that Erasmus has had, and how it has assisted so many students to go abroad, but what makes it interesting to me is the following fact: twice as many Erasmus students study in the UK than go from the UK to the continent to study.
Is this due to limited aspirations? Or the confidence in our own quality of educaiton on offer? Or a cost factor? (Europe is still percieved as being more expensive). Personally, I think that British students are confident in their own education system, plus the majority of them will not be fluent in a different language, and take it for granted that travel and working abroad will happen, but after graduation.
It will be interesting to see how it changes in the future....