Hi Caila25 - You've been told what will happen to your boyfriend over this unfortunate business. But there is one thing in mitigation that may help when he goes to court.
I worked in a bank dealing with customers changing banks and transferring their Direct Debit details. Now banks and building societies must liaise with each other when dealing with clients Direct Debit details.
You said earlier:-
'I changed bank details and gave new ones to insurance but they didn't change them so last payment defaulted as it came from old bank with no money in'.
Your new bank should have instructed you to leave enough money in your old account to cover payments due from Direct Debits, because they can take a little while to set up. Then, only when they have your new account fully up and running with DDs coming from the new account would they have advised you to close the old account, and to transfer any amount left to the new one.
If your new bank didn't tell you this, get them to admit they failed to tell you, in writing, and that can be produced in court as mitigation. Unfortunately if they did inform you and you chose, for whatever reason, to ignore their instructions then I'm afraid that is another matter.
I am sorry for your predicament which I think is down to your naivety more than anything else. Although adverts put out by the banks make transferring seem easy, I know that I would think twice before I ever change bank accounts. My advice to anyone else would be, do it when you're feeling flush, because if you have a lot of DDs, then money to cover them needs to be lodged in both the old and new banks.
Companies all act at different speeds when it comes to acting on new DD instructions.
I do hope things work out as best as they possibly can for you and your boyfriend.