It's very easy to do yourself.
The biggest source of error is the actual interest rate charged. They tend to get the arithmetic and payments received correct.
Stage 1 - Did they charge the right interest?
This might seem daunting at first, but you get the hang of it very quickly.
1) Read your contract to see if what the rate should be e.g. ECB + 1%
2) Check the statement to see that they did apply the right rate. You will get the ECB rate
here.
3) Check each monthly interest charged. You can get a very rough idea as follows:
Opening balance x interest rate /12
Or you could set up a spreadsheet as the lenders charge the interest on a daily basis, so the interest in shorter months is less than in longer months.
Stage 2 - Did they credit all payments to your account?
Check the amounts received against the payments made from your current account.
A random check should show that they are ok.
Stage 3 - Did they give you the correct Tax Relief at Source
Stage 4 - Were the other charges justified?
Did they charge you the correct amount for insurance?
Did they charge you penalty interest on arrears?
