I am currently dealing with claiming back PPI charges on my husbands loan through Funding Corporation (long since repaid). They have made us an 'offer' which is £500 more than I was expecting but their method of calculation is a bit unclear. We are asked to sign the 'offer' to say we accept, after which a cheque will follow. I have 3 questions about this and would really appreciate all your expert guidance!

1. Is there a spreadsheet template to work out more or less whether their offer is acceptable? I do not trust them to have been accurate!
2. They have deducted basic rate tax from the calculation which they say will be forwarded on to HMRC. I just find this a bit odd as have done numerous PPI claims / CPI claims and I just don't remember this ever being part of the process before (which may be my memory) and I don't really understand why what amounts to essentially a 'refund' is anything to do with HMRC? Could anyone verify this is correct?
3.There are also a number of 'unfair' charges on this account of £20-£30, even after 2006 when I understand regulation came in restricting it to £12 or less. If we accept this offer of PPI are we accepting that everything is resolved with Funding Corp? Or can we wait to receive PPI money and then write again complaining regarding the charges?