The high cost of living, the bad weather, the crippling taxes, the interference from the nanny state, to name just a few...

Hope they haven't come to India.

The fact that Londonistan is becoming an Islamist enclave and they want to get out while they can. Note that I did not say "Islamic," I said "Islamist." Many Islamics (Muslims) hate and fear Islamists, because moderate Muslims are the likeliest to be killed under Islamist states.

I think it's probably due to a combination of factors. The increasing crime rates coupled with the yobs that seem to roam the street of the majority towns and cities is likely to be one of them. Many people leave seeking a warmer climate (hence the huge amounts of expats in Spain) and others because of the expense of everyday life which is higher here than in many other nations. There is arguably a problem with overpopulation (there certainly will be one in future) which had led to an increase in competition for jobs and some may have left to seek a career abroad. Another thing that needs to be taken into consideration is that the high immigration into Britain means that there are also many long term immigrants choosing to leave the country. We have had many people come in from Poland, Romania and other countries trying to build a better life. Many haven't found their desired lifestyle and would rather return to their homeland than be exploited by British corporate bosses.

I can't answer for the time period that you mention, but as a Briton living abroad I may be able to give some insight. The primary reason my wife and I chose to leave England and live abroad was the climate - I suffer from arthritis, which is worse in the winter than the summer. Coming to live in a climate where the winter is similar to early English summer has led to my intake of drugs to be reduced to a tenth of what I used in England. Ironically the climate has caused a recurrence of the asthma that my wife suffered from as a child and we are currently discussing whether we should return to Britain for the sake of her health. She wants to stay here and I think we should return. Obviously life style and cost of living are factors - eating out is cheaper, as are alcoholic drinks and cigarettes and the cost of food and housing are similar to England. We have no television licence, local taxes for a year would only pay about a month's Council Tax and my car tax costs about €50 for a year. Other taxes weren't an issue because my pension is paid by my former employer in England, so I still pay UK income tax. The political situation wasn't an issue because I honestly believe there is so little between the parties that hardly anything would change, regardless of which of them is in power.