Heavy rainfall, mosquito infestations and flooding are bringing fresh misery to beleaguered survivors of Hurricane Irma, a week on from the storm which brought devastation to the Caribbean last week.

But while the British government continues to face criticism for what some see as a slow reaction to the plight of its overseas territories, a volunteer-led response is now under way in locations such as the British Virgin Islands (BVI).

Simon Roberts, a carpenter who was resident on the BVI’s largest island of Tortola for more than a decade but evacuated with his wife and children after the category-five hurricane hit, was this weekend preparing to return with a dozen tradesmen, bringing tools and resources in by boat from the US.

“Sanitation is now a huge issue, so we are going to be getting stuck in to helping with that,” said Roberts. “Most people there have a house on a concrete slab, a cistern and ‘soakaway’ system for their toilet. So the basic plan is to start rebuilding shelters on those slabs and to get guttering in place, so that they can start collecting fresh water again.”

Tortola resident Chuck Krallman told the Observer: “One hundred per cent of the country has been devastated. The logistics of moving supplies and aid is extraordinarily difficult and expensive. Thousands of people are living in ramshackle buildings with no walls and need to leave. Many people have lost everything, have no cash or clothes, and don’t have the money to leave.”

Power is gradually being restored to many parts of the BVI, including the territory’s main hospital on Tortola, but a curfew remains in place from 6pm to 9am, and residents have been asked to stay off the roads unless necessary.

Many current and former BVI residents are using social media to mobilise resources and circulate lists of urgently needed supplies, including generators, blankets, bed linen, mosquito tablets and construction materials.

Other efforts include those organised by Richard Branson, whose Caribbean home on one of the BVI’s 50 islands was badly damaged.

On his website on Friday, Branson wrote: “While we are incredibly thankful for everything being done to help the BVI communities, more help is needed … These islands now really need the level of support only a large organisation with significant disaster management experience can provide to come in and help.”

The Foreign Office said this weekend that it had arranged military-assisted departures for eligible persons from the BVI and was putting similar arrangements in place for other affected overseas territories. In addition to Royal Marines who are on the ground providing security, Public Health England is sending three specialists to work with the chief medical officers of the territory.

The hurricane could prove to be a catalyst in the longer term for a rethink of the economic and social model of territories such as the BVI, as well as Britain’s relationship with them.

Dr Peter Clegg, associate professor in politics and international relations at the University of the West of England in Bristol, who has advised Caribbean governments and UK ministers in the past, said that the relatively high GDP figures for societies such as the BVI masked income diversity.

“A situation like this is likely to highlight that territories like the BVI are vulnerable and cannot rely on the benevolence of the UK. Their great hope, going forward, was exporting fish to the European market, but all territories are now quite concerned about the implications of Brexit and how that may impact free movement and also EU aid.”

Clegg said the UK government had been “playing catchup” since the hurricane. “These territories do not have the physical capacity to respond to a hurricane. They are vulnerable, with limited infrastructure, and the UK really should have stepped up more quickly.”