Thanks SaySomething.
I know that you are being helpful and I know that I can be awkward!! The reason for the data disclosure request is because I want to see all relevant bank records. I suspect that somewhere in this pile, there will be data of interest/benefit to me. It could be, for example, an internal e-mail between two bank colleagues. I have no way of knowing such dates & times & senders. The point being that I am not asking the bank to supply me with specific information - I am asking them to supply all information.
For example, the pack I got had no e-mails - zero, nil. This is simply not credible - as I myself have sent them many e-mails!

My sense is that I should write to the bank and cc the data commissioner. There is a clear issue with the bank's compliance with the GDPR - in my opinion, they have either deliberately not supplied relevant information or they haven't put in place sufficient procedures to ensure that data request are dealt with properly. Either scenario isn't great by the bank - hope the Data Commissioner isn't as rudderless as the CBI in knocking the bank's into shape!!
It will be interesting to see what happens!!