Help calculating how much interest I owe

leightonr

I wonder if anybody is able to help me. I borrowed some money from a friend that I have just been able to repay.
I borrowed:-
£35,000 on the 1/12/2005 and
£15,000 on the 14/08/2008.

My friend withdrew the money from their Abbey Esaver account so we agreed that when I repaid I would pay interest equal to what the money would have earned in their Abbey eSaver account for the £200,000+tier.
I have today repaid the £35,000 and £5,000 of the £15,000 loan.
However, I don't know where to beging to work out what interest I should reapy them. It doesn't need to be that accurate but I don't know how to even get to a ball park figure - can anybody help or point me to some resources where I can work this out? Thanks

cashbackproblems

WHat is the interest rate on his account, then it should be pretty straight forward.

leightonr

That's the problem - I can't find the historical interest rate anywhere. If I could find historical interest rates for another hiigh deposit UK savings account then that would help.