I'm glad Nationwide are exposed here for what they are, ie worst sharks in the pack and not what they want us to believe, ie a 'friendly' building society. I'd say expect the unexpected from them. I can't go into details, as I have an outstanding County Court Claim against them for over 4 grand (inc. interest and costs) but I will tell once it's settled. In the meantime, go to the DPA website and download a complaint form for not complying to a S.A.R. request within 40 days and let things nicely take their course. The Data Information Commissioner's Office knows all about their tricks plus they have just had a fine of nearly £ 1 m for the loss of the laptop with details of 000's of customer id's.
BTW, don't fall for the £ 5 per page trick (they try that one first). As a previous poster mentioned, just send them a letter with the heading S.A.R. (Subject access request) asking for 6 yrs statements. They'll write back a few weeks/months later asking for £ 10. It's all to do with buying time-don't let them! The more complaints they get, the faster they'll have to act in future. otherwise another fine will do nicely, thank you.