About to apply for citizenship; days outside UK

After 5+1 years living here, I'm getting ready to apply for citizenship.
I've passed the test, I've got the referees, I've got the money.

My only doubt is how to prove I've been in the UK the required days (indeed I've been). I have travelled quite a lot on holidays, however not even close to the maximum days allowed.
My passport has a few stamps, but not all of them, since about three years ago I enrolled into Iris to speed up the immigration process, and therefore I don't get my passport stamped every time I come back to the UK.

I've read that I could show a letter from my employers showing that I've been working for them at their offices, but the problem is a couple of the companies I worked for during the first years no longer exist.
I've got all my payslips and P60's, will this be enough?
A friend suggested that I could use credit card statements to show that I've been using the card in the UK. Is this true?

Thanks!

You can get a printout of the records with IRIS. Just email IRIS at irisinfo@homeoffice.gsi.gov.uk with the passport number, name etc and they will email a sheet which has entries on IRIS.

If you are within the limit of days, don't worry. Put the dates to the best of your knowledge. The HO can always verify it using their systems.

Thank you very much, I just sent the mail to them.