Most people have gotten into the habit of checking with places like Equifax before trying to apply for credit of any sort, mostly because the probability of them obtaining the credit or having their application approved is highly dependent on the information received from Equifax.
What do you do when you know that your credit rating is favorable yet your application is still declined? Most companies do not offer definitive reasons for the application being declined, they rather give a generic answer or refer you to Equifax, and then you land up in a tug of war between the provider and Equifax while you try and find out the real reasons.
According to the article on The Guardian it could be as simple as you applying for credit too often, like when you apply for a phone and get your application accepted only to find that the phone is not suitable for your needs and apply for another one before cancelling the first one. Each time you apply for anything a log of the credit search is recorded and some providers will hold this against you by stating that you are a high risk client.