In reply to Tommyads:
Update:
British Gas have cleared this bill and told me within 16 days I will receive an email showing £0.00 account.
It's frustrating that web chat will give you a copy of the conversation for your records, but if you sort something over the phone (to get it done properly) you just have someones word that if you do nothing, in 16 days you will receive an email with your pardon.
So I am going to speak again with British Gas on web chat. I want to get the numbers and dates involved for the time I was there and for this additional bill. I want this all in writing showing how he has used my information and prompted unnecessary billing.
So there's no money leaving my account, now I just need to work on getting the deposit money coming in.
I have formally given my landlord 10 days to pay me back so this should get things moving. I will call the deposit scheme if I have time after my web chat, but it does say the landlord claims the deposit.
I haven't been able to get hold of Citizens advice yet (they are difficult to reach and I have been at work) but the website has been helpful.
Thank you for the replies. I'll hold off on the name and shame, fraud case and blackmailing for the time being. I'm not comfortable with any of that until citizens advice show me how to pull it off.