Yes, they certainly are!
There is a period of 15 working days after the year end and before the audit when "every account, duly made up and balanced and all the relevant account books, deeds, contracts, bills, vouchers, and receipts must be open to inspection by all interested persons, who may make copies or extracts without payment".
The exact dates for inspection must be published in advance.
Otherwise, it should be possible to ask for specific documents through Freedom of Information. And good councils will be happy to let electors know about their accounts provided requests are reasonable and not taking up excessive amounts of staff time.