I don't know. Bank of England base rate is at record low levels, just 0.25%, so with the HUGE amount of collateral offered they may well of gotten less than a single percent interest rate on the loan.
I used to work in merchant banking / general finance in the City of London however left the sector after the financial crisis, although I do still have a lot of friends, contacts and even family members still working there currently. I also worked and managed accounts for large international companies, umbrella corporations and mid-size companies with Coutts before, and can supply proof if need be.
I know for a fact CIG won't be getting a 0.25% loan, simply the fact they were forced to get a loan from Coutts is worrying, for commercial loans it's the bank of last resort because you can get loans way way way cheaper from other commercial banks such as HSBC Business and Barclays Business. People use Coutts for it's privacy and discretion, and pay through the nose for it. Like most commercial banks they have an annual 1% flat management fee for all secured loans (even higher for unsecured ones). This means ontop of the interest rate CIG is paying 1% of the value of the loan every year for the borrowing privilege.
Also the collateral for the loan that CIG have put up is fairly pathetic, they wont own the offices they are developing in and surely have long leases with the landlords (promised future debt, which is priority for repayments) that devalue the assets massively. They don't even have a working finished product, let alone multiple products. It's also a very new company with a huge number of liabilities and only a few income streams which are highly variable, such as the ongoing kickstarter fundraising. There's also the fact that Chris Robert's previous software and film enterprises mostly ended in failure or needed to be brought under financial control by outside bodies such as Microsoft...
They'll be paying top-whack in merchant banking terms for any commercial loan, much higher rates than huge established companies like Coca-Cola and Apple. No doubt they went with Coutts because Chris and Sandi use the bank to hide their substantial personal wealth which I'm lead to believe is in the millions. This is probably why Coutts agreed to lend to them in the first place also, due to their personal history with the bank.
Coutts actually do a specific 1-12 month business bridging loan for tax purposes, which I believe is the specific loan CIG took. It's secured and good for up to 70% max of the estimated value of the company, which gives you an idea how much they think the overall company including all it's assets and minus liabilities is worth. The loan runs at about 2.25%, plus the 1% annual fee (which if CIG pay it off in total within the 12 month period they will only have to pay once). There's also some brokerage and accountancy fees related to initial setup that they have to pay, around a fixed £75,000.