When David Cameron gave the nation an extra day off in honour of the wedding of a prince, he may not have reckoned on the impact. Far from pinning up some bunting or jostling for elbow room around the biggest flatscreen in the village on 29 April, many British people plan to leave the country and abandon the spectacle to the tourists.

Bookings for foreign breaks have shot up, while online holiday companies are reporting that the number of people searching for April getaways is double last year's. Travel agents are reporting from 30% to 56% rises in interest in their holidays, while Hotels.com says that the number of people searching for holidays for the week ending 29 April has increased by 212% compared with the same time in 2010.

Thomas Cook has put an extra 100,000 sunshine breaks on sale to meet demand, a third more than usual, while Ryanair has reported a 65% increase in bookings. "It's a bonanza for the foreign travel industry, which I'm sure the prime minister wasn't expecting," said Lonely Planet's Tom Hall, who has been inundated with readers looking for advice on the best destinations. "And it's an absolutely lovely time to be in the Caribbean." Hall added: "There is a huge degree of interest making the most of the extra time that's being offered. As pretty much anyone who works will back up, an opportunity like that is not to be missed. And, of course, hoteliers in this country are facing an influx of tourists coming into London for the wedding, so it's a good time to leave town."

The extra day off on Friday, 29 April, means that millions of workers will enjoy two successive four-day weekends in quick succession: 22-25 April, taking in bank holidays on Good Friday and Easter Monday, and 29 April–2 May, taking in the royal wedding and the May Day bank holiday, with only a three-day working week in between.

"Holidaymakers now only need to take five days' annual leave to benefit from a 14-night holiday,'' said Richard Calvert, managing director of Thomas Cook holidays, welcoming it as "great news for savvy travellers". So far, the most popular destinations are places with plenty of early summer sunshine, such as Turkey, Egypt and the Canaries. European republics are also popular, especially with independent travellers. The travel firm Skyscanner said that Germany was the top destination for escapes over the 29 April weekend.

For those keen to avoid the wedding but not able to leave these shores, an alternative event has been set up by a Welsh cultural group: the Escape The Wedding Camp at a campsite near Machynlleth. Balchder Cymru (Pride of Wales), a group set up to promote Welsh consciousness, is considering staging a march through Machynlleth on the day to celebrate the area's links with their preferred Prince of Wales, Owain Glyndwr, who was crowned in the town in 1404. "We are giving people an opportunity to escape the razzledazzle and media hype that will take place when the wedding takes place. Not everyone will be celebrating," said a spokesman for the group.

On Oxford Street yesterday, a shop owner who didn't want to be named admitted that there was little interest in Kate/Wills memorabilia. "Postcards are doing OK, but it's a lot of Brits writing jokey, bitchy messages."

Tourists were buying union-jack-emblazoned products for their kitsch appeal. Paula Hilton, 26, from Lancaster, in London with her mother Elizabeth, 56, for the weekend, was buying her son a model of a London taxi. "I wouldn't come near London on the day," she said. "I'll have a look at the dress in the paper or whatever, but I'm not invited so I'm not watching!"

Many Londoners, meanwhile, are hoping to cash in on outsiders' enthusiasm. The city's hotels are racking up prices to take advantage of a possible 500,000 foreign visitors, while the websites Gumtree and London Rent My House have huge numbers of people offering to rent out their homes – while they, presumably, seize the opportunity to take a holiday.

The writer Anthony Holden is one of those who have opted to join the anti-monarchist exodus: "I am certainly planning to flee the country, due to my republicanism, general hatred of the news coverage and the fact that because of Easter weekend it's like the dead week between Christmas and New Year. I shall go somewhere to the sun and work on my new book," he said.

The campaign group Republic is hosting one of several "anti-royal wedding" street parties. Its spokesman, Graham Smith, said he'd expect a few hundred people at the London event.

"We expect the majority in the middle who are largely apathetic to just go on holiday to ignore it that way, and I hope they have a good time. At least 20% of the population are opposed to the monarchy, and many more simply don't care about it."

Polls and complaints to the BBC about coverage before the event showed an unexcited nation, he said, adding: "The public holiday blows a hole in the idea that the wedding will be an economic boost for Britain. The CBI has calculated an extra day off would cost the economy £6bn."