Just arranged an unsecured loan for £15k with HSBC, payable over 7 years maximum. That is the maximum they would agree to as I am a "stranger" to them. My banking history is about as good as it could be with no black marks against my credit history and I prepared a polished business plan for them too, but £15k was as far as they would go. Anything above that figure and they wanted security or I need to have banked with them for many years and built up a history. They also let you repay over a maximum 11 years if you borrow over £15k.
All I have to do is move my current account to them. They will also consider any further requests next year when I have some history with them but hopefully that won't be necessary.