Interest by instrument and CGT

All

I am hoping for some advice on how to get the below information, For CGT returns you need to do both of the following:

Share matching and the allocation of attributable costs by position

Share matching - i am assuming you either export from the next Invest reports or copy and paste the daily statements for CFD positions into Excel? then use this website for both CFD and Invest accounts

http://www.cgtcalculator.com/calculator.aspx

For the allocation of interest all i can find is the total interest i have paid monthly, no breakdown by instrument or even when an instrument is closed no offset of the interest in the gain so i cannot work it back. Any ideas on what people will be doing for this?

Thanks
AB