Coinfloor are the UK’s longest running (founded in 2012) and most liquid Bitcoin exchange.
Security: All client bitcoins deposited, withdrawn or held with Coinfloor are stored safely offline requiring multiple signatories to release. They also use two-factor authentication for further protection. They regularly publish audits for their clients to review the balances held on their behalf.
Fees: Creating a Coinfloor account is free of charge. Storing bitcoins and bitcoin cash in Coinfloor’s secure vaults is also free of charge. Trading on Coinfloor Exchange does not incur fees.
For fiat operations, Coinfloor charge a flat deposit and withdrawal fee to cover Bank charges for processing the transfer, and a percentage fee (between 0.34% and 0.38% depending on volume) calculated based on the 30 day deposit and withdrawal volume in the relevant currency.
Bitcoin and bitcoin cash deposits are free of charge and there is a minimum deposit amount. There is a nominal charge for bitcoin and bitcoin cash withdrawals to cover miner fees.