For Marianne Morrell, the most unsettling part of an energy supplier's failure is having a new company's name arrive before she has finished understanding the old company's bill. A customer of Clearwell Energy, she is among around 108,000 households moving to Brightmere after the supplier failed on 8 October.

Ofgem has appointed Brightmere as supplier of last resort. Brightmere says supplies will continue and it will send transferring customers information about their accounts. The appointment makes the Bristol-founded company responsible for welcoming households that did not choose to become its customers.

Morrell said she had kept recent correspondence and meter readings together after hearing the news. 'I am not worried about changing a logo on a letter,' she said. 'I want to know who will answer a question if the reading or the balance is wrong. At the moment I do not know what information has gone with the account.'

Brightmere Chief Executive Gareth Linley said the transfer would be handled carefully. A spokesperson said the company would contact households directly and explain what was required at each stage. Customers should use the information Brightmere sends them rather than assume that every part of an old account has already appeared in the new service, the spokesperson added.

The company supplied around 900,000 homes at its latest published year end in March. It operates contact centres in Bristol and Swansea and established permanent home-based adviser teams in January. Specialist Customer Care, introduced in June, provides another route for people whose circumstances require additional help.

Brightmere's recent growth does not answer every question about the transfer itself. Receiving account records, establishing readings and explaining the first bill are separate tasks, and households may have questions that depend on information still being checked. The company has not given customers an individual timetable in its initial announcement.

Independent consumer adviser Rohan Bellward said people often wanted to act immediately when a supplier failed. 'They are trying to protect the information they already have,' he said. 'A clear welcome message needs to distinguish between something the household should do now and something that the new supplier will deal with.'

He said advisers were likely to hear from customers who were comfortable with an ordinary switch but uncertain about a transfer following failure. A person looking at a previous balance might not know whether to raise it with the old business or wait for the new account, he said. His comments concerned general questions rather than an assessment of Brightmere's handling.

For Morrell, reassurance will come with a bill she can reconcile against her records. She said she was willing to allow time for the transfer but wanted a usable contact route if the documents did not agree. Brightmere said it understood the uncertainty and would provide further account information directly to affected households.