Help please, don't know where to start!

newbs68

Hi, we had loans and credit cards between 1994 and 2006 with various institutions. Our bank was/is Lloyds but we've had cards with MBNA, Capital One, and a couple of others of which I cannot remember the names. We also had a five figure loan with Northern Rock. Since paying it all off and moving house in 2006 we got rid of all our old statements and paperwork.
Where do I start investigating if I can even think about making a claim?
I think an Equifax credit report but that only went back six years which is of course useless as we've not had any loans since.
Please, please someone point me in the right direction.