Mistakes on credit file

Good evening everyone
Apologies for the long post ahead but we would appreciate advice on this
My husband and I are in the middle of buying our first house (wish us luck!!)
We found one made an offer got accepted (yay!)
Started the whole mortgage hunt.
Searched online and found some rates we really liked.
Nationwide was one of them
Called them and went through the entire process where they took all the required information for an hour
And finally got to the hard credit search stage.
We were quite confident as we have been with experian for a few years and have been steadily building up our credit score. No late payment no overdrafts no loans. 1 credit card which we had been religiously paying back every month to bring the balance back to zero..
And Nationwides system declined us
Even the mortgage advisor was puzzled as we were applying for a mortgage well below our limit
My husband earns 55k and we were applying for a 150k house with a 10% deposit I get carers allowance
He asked us to contact the credit agency(EQUIFAX) directly and check whats wrong as they are unable to check this themselves
I called them and they sent us a link via email. Which we used to sign up and started going through our credit file and score
We found some major shady stuff in there
1. In Dec 2016 it said we missed 3 BT payments in a single month (which is a bit absurd as we only have 1 account with them)
We were sure that we had been paying them on time and just to confirm we called bt and they said yes there are NO missed payments
2. We found a barclaycard on the file close to its max limit (£8500) upon further inspection we realized that it belonged to my husbands brother!.with a completely different date of birth next to the entry.
3. Also an EON account belonging to my brother in law hanging around my husbands credit file
Now points 1 and 2 would have raised major red flags on any mortgage lenders system
We contacted Nationwide and told them about this mess. Told them these items are only in the equifax report . Our experian report is clean and can they not use other credit ref agency
They apologised and said there is nothing they can do. Their system is such that it randomly uses equifax/experian/callcredit and gives them a decision. And there is no way to overrride this.
I was quite furious at that point as to why a company which has such a flawed way of entering data is given the opportunity to influence the decision making process for Nationwide
I made an official complaint to their customer services. And got a reply from their complaints officer the next day
They suggested I go for an appeal
I went for it . Wrote them a lengthy email explaining the situation. The complaints team said the decision is being made by the underwriters now and they are asking for a few more documents AND a letter from equifax admitting they made a mistake
HA!
Like any sane company would blatantly admit their fault
In the meantime we had been in contact with equifax pushing them to correct the mistakes
Our corrspondence was through telephone and email. I asked them to send me a letter but no response from them so I sent a copy of all the conversations that I had with equifax to Nationwide
I called bt and asked them to send me an email clarifying that we have not missed any payments and there is a mistake on the credit file. I sent this to Nationwide as well
After 5 days we got an email . Nationwides underwriters had rejected our appeal.
We felt the house slip away from our fingers
I was upset but determined for us not be punished for someone elses mistakes
Started messaging Equifax on Facebook. Twitter. Emailing them . Basically trying to grab anyones attention to sort out the mess they had made. It paid off and we got an email from them that they have removed the errors. Hallelujah!!
Things went pretty straightforward from there. We could not go back to Nationwide but went with barclays instead. Their rates were a bit higher but we were satisfied with how they handled our application.
Our mortgage offer was issued in 10 days and we are just waiting for the legal work to wrap up.
BUT
their rates are higher than nationwide so we will be paying more than we would have if our mortgage was with Nationwide
Now this whole mess created by equifax has been simmering away in the back of my mind for a while
I am aghast as to the poor standards of this agency. They can mess around with people like this and influence major life decisions
We have been through so much stress throughout this period and I wonder if others have been affected as well.
To put salt on our wounds today I got an email from Equifax offering us £150 as compensation and that this is their final offer but we are welcome to contact the financial ombudsman for complaining
I mean the company did some serious damage to us
Financial no doubt as we will have to pay more now but the stress has been unbelievable. I am seriously contemplating going through the process
Do I have a case against them
What should we do
Is there anything we can do to strengthen our side of the story.
Any tips from moneysavers??
Thanks for reading my rant/story and thanks in advance for your responses x