Experian letter, are they phishing for business or is threat real??

Scam

The job of a credit reference company is to let duly accredited organisations like banks, building societies,
credit card and public utilities access your record online to check on your creditworthiness.

This is a classic scam email. It doesn't say whether the person who accessed your account was entitled to to do that or not. It is classic scam behaviour use language that sounds worrying but actually means nothing.

Quite a number of organisations have been accessing my credit record online doing all the usual checks that surround a mortgage application.

Bin the letter. Do not respond.

Your credit history is not just about what loans or credit cards you have had, it states that bills were paid on time or not. I have always trusted Experian but if you do not want to check your credit score then don’t.

I would never access a site direct from an email even firms I know.