My staffordshire bull terrier puppy who is 12 weeks old keeps attacking the cat flap, she is not too bad if door is open but if door is closed she goes mental, how can we sort this?

When you are around you need to keep a close eye on the dog. Use closed doors or gates to keep it in the same room as you are, and perhaps as I do, a short chain fastened to the computer desk. If you catch it in the act, give it a sharp ''Ah, ah, ah!'' and offer it a chew toy. When you can't watch it, crate it.

For more help, see the sticky at https://www.askmehelpdesk.com/dogs/information-articles-our-dogs-expert-labman-53153.html#post251802

I would definitely take labman's advice as he knows what he is talking about.