compensation -- data protection act breaches

prb1

about four weeks ago i missed a payment with a loan i have with
Nat west, they contacted a previous owner of the house
where i live and own (i have lived here for ten years) they telephoned
the person and gave them a lot of my personal details
(when the loan was taken out,the account number,the amount
in arrears and more. The person lives a few miles away and visited me and my wife to tell me what had happened. i was very surprised and embarrassed that the bank gave a third party all this information.
The bank has written to me three times apologising
and telling me an investigation is underway (the person who received
the information also complained to the Nat West bank). Should I claim
compensation and how much ? (the person apart from being a previous
owner is not connected to me in anyway)
Any advice welcome
thank you phil