http://www.callcredit.co.uk/business/complianc e/Third-Party-Data
From this link, it seems that you needed to have requested to Opt Out when you first applied - I'm guessing that when you applied you either signed or agreed to normal terms & conditions which would have been the equivalent of an opt in.
Therefore, the bank has only searched you, but by default would have got details on your husband.
Also, it is worth noting that even if you have opted out, I reckon that the bank would still have rejected your overdraft as CCJs would still show up as they are public record and not private records (same as Voters Role info)