Thirty years ago, the percentage of the British people who vacationed in foreign countries was very small compared with the large percentage of the British population who travel abroad for vacations now  Foreign travel is, and always has been, expensive from Britain
Ttherefore, British people must have, on average, more money to spend on vacations now than they did 30 years ago
If more of the British people of 30 years ago had had enough money to vacation abroad, more would have done so.