Forget hopes of a government U-turn on leaving the EU, say UK industry leaders.

The challenges posed by Brexit could outweigh any advantages even for the booming inbound sector, but there is “no real feeling for overturning” the decision, say senior industry figures.

Inbound tourism is enjoying a boom thanks to the fall in the pound, with Tourism Alliance director Kurt Jansen telling a forum on The UK Tourism Industry Post-Brexit in London last week: “You give people a 15% discount and they are incredibly motivated to come [to Britain].”

UKinbound chief executive Deirdre Wells said: “We’ve done well out of the fall in the pound, but it won’t last forever. Increased costs will find a way into the supply chain.”

She told the forum: “We’re now into a very challenging period. The industry contracts potentially 18 months out.”

Wells joined fellow sector leaders in dismissing the idea that the Brexit decision can be reversed. She said: “The politics haven’t really changed. It’s our job to make sure the government delivers the least damaging Brexit possible.”

Jansen, whose Tourism Alliance embraces outbound and inbound travel and includes Abta, said: “There is no real feeling for overturning Brexit. A crude argument that the whole thing is wrong just does not play.” But he said: “Politicians are desperate for people to tell them how to make a success of Brexit.”

Heritage Alliance chief executive Lizzie Glithero-West said: “The number of civil servants working on any of our areas is diminishing. The most useful thing we can do is help them. We are more likely to be listened to.”

KPMG public policy director Mark Essex agreed, saying: “If you get an audience with [Brexit Secretary] David Davis, you can try to convince him he is wrong or you can say, ‘We understand what you want to do’. If you offer help you’re more likely to get a second hour.”

John Guthrie, employment policy advisor to the British Hospitality Association (BHA), warned that free movement of labour from the EU to Britain would end “probably from December 2020, but conceivably from March 2019”.

He said: “The sector is absolutely stuck between the economics and the politics of Brexit.

“Businesses should assume a significantly more restrictive immigration settlement, and it will have an impact [because] 96% of EU workers in UK hospitality would not get into the country [if they were] from outside the EU.”

Jansen identified the biggest post-Brexit challenges as being to “retain EU travel arrangements, maintain access to EU workers and replace EU funding programmes”. But he suggested there would also be post-Brexit opportunities to boost tourism – for example, using the government’s air connectivity fund to start new routes.

EU rules prevent funds going to airports with more than two million passengers a year. Post-Brexit, Jansen said: “The government will be able to pump-prime funding for new routes to the regions.”

Conservative leaders were convulsed by a row about whether Britain should remain in the EU customs union this week amid reports that pro-Brexit members of the cabinet could overthrow prime minister Theresa May.

Wells said: “I urge we stay in the customs area. We need an efficient and welcoming border. We need light-touch processing for visitors. We need a business-friendly system for workers.”