More than a thousand people are feared missing, including at least 33 UK tourists, after devastating flash floods tore through villages on the Nepal-Tibet border, killing 165 people.A 13-year-old girl is among the British tourists who are unaccounted for after catastrophic flooding likely caused by a glacial collapse in the Himalayas, which engulfed entire villages in Nepal’s Rasuwa region.The mountainous area is popular with hikers and trekkers from around the world as well as pilgrims who cross the Himalayas on journeys to sacred sites such as Mount Kailash and Lake Mansarovar in Tibet. As rescuers continue to search for survivors and drop off emergency supplies to isolated communities, the UK government says it will do “everything it can” to help British nationals affected by the flash flooding.As the death toll is expected to rise, here is what to know about travel to Nepal and Tibet.Live: Nepal flash floods latestWhat has happened?On 26 August, major flooding in Nepal’s Rasuwa district and the border with Tibet has devastated communities living in the mountainous region, with at least 800 foreigners still missing.Widespread destruction has been caused, with buildings, roads, other transport and communications infrastructure severely damaged. Videos have shown a wall of water crashing through river banks, collapsing bridges, tearing through homes and other infrastructure in villages along the Bhotekoshi River.Similar footage from the opposite side of the Nepal-Tibet border also showed people fleeing before a deluge of rock, mud and water engulfed the area.How many tourists have been affected? The latest update from the Nepal Tourism Board says 644 tourists are still missing, according to various trekking and travel companies.Indian nationals make up the highest missing persons count, with 178 unaccounted for, followed by 127 domestic Nepalese tourists.Many of the Indian nationals are believed to be Hindu pilgrims who were trekking towards the sacred site of Mount Kailash in Tibet.Additionally, 53 Ukrainians, 51 Malaysians, 65 Americans, 35 Australians and 33 UK nationals remain out of contact, the notice says.Houses lying in mud after the flash floods at Devighat, Bidur Municipality in Nepal's Nuwakot district (AFP/Getty)Sunil Sharma, a spokesperson for the board, said: “We are coordinating with the relevant authorities for their search and rescue.” The Nepal Tourist Police also told BBC News that they are continuing to collect information from tour operators about the tourists who had travelled in the area.Some tourists have been rescued, the national police and army have said, although not all their nationalities have been confirmed.Around two dozen tourists had been rescued and brought back from the Rasuwa district to the neighbouring Nuwakot district on Thursday, while 21 Indian nationals were also being brought back to Kathmandu.What does the UK government say?The UK’s Foreign Office (FCDO) said on its online advice page that the “situation may change rapidly”.“If you are travelling in the region, follow the advice of the Nepalese government and local authorities and be alert to the changing situation. The Nepalese government has established a toll-free emergency Nepalese language number, 1234, and a dedicated hotline 1144 accessible in Nepal.”If you are affected and need assistance from the UK government, call:from Nepal +977 (0)14237100 from the UK +44 (0) 207 008 5000 It also advises British nationals in Nepal to sign up to get email notifications for updated information. A collapsed bridge along with houses lying deluged in sludge after flash floods at Devighat, Bidur Municipality in Nepal's Nuwakot district (AFP/Getty)If you are in the UK, but are concerned about someone in Nepal, the FCDO helpline for information is 020 7008 5000 (24 hours).The FCDO also warns of heavy flooding and landslides in Gyirong County in Shigatse, Tibet, near the Nepal border.“There is an ongoing risk to life from flooding, landslides and infrastructure damage. Roads, power supplies and telecommunications have also been disrupted.“Exercise caution and follow the advice of local authorities,” it said.Can I cancel and get money back on my holiday?As the FCDO has not warned against non-essential travel to Nepal, there will be no special circumstances in place to be able to cancel a trip for a full refund.The conditions for cancelling your trip will be dependent on your holiday provider, so it’s best to contact them if you’re looking to postpone.There is no obligation for companies to refund bookings if you want to cancel, and you will not be able to claim on your travel insurance due to safety concerns unless government advice changes.If you do have travel insurance, some policies include natural disaster cover for an event that prevents you from reaching your holiday destination. Check your insurance policies and speak to your insurer to see where you stand.Read more: British girl, 13, among 33 UK tourists feared missing after Nepal flash floods