Dog adoption in Portsmouth, England Black labrador Dog "Cooper"

We bought Cooper when he was 8 weeks from a labrador breeder that we have bought from before. We took him to puppy classes where he learnt the basic training commands. When Cooper was 2 we had to put to sleep our old labrabor and a few months after that my eldest daughter and her boyfriend moved out. Not long afterwards Cooper began showing signs of anxiety especially when strangefs knocked the door or walked past the house. He would constantly bark and it became difficult to stop him. He also began randomly barking at me for attention. Whilst out walking with him he would bark at anyone I stopped to speak to. I had a dog therapist come to see him and she agreed he was suffering with anxiety and he began a course of Prozac medication which improved his behaviour a lot.unfortunately I couldn’t afford to carry on with the trainer and so he only had the medication for 6 months. Cooper continued to bark constantly at strangers entering the house so I would have to separate him using a stair gate. He continued barking at anyone who walked past the house and at any noises he would hear. He would bark at me if I tried to use my treadmill or exercise bike. I started to feel trapped and depressed with his behaviour. A couple of months ago as I was leaving the house with him to go for a walk he saw a dog walking past our house and pulled on the lead causing me to fall over and let go of the lead. He ran over to the other dog and bit him. The other dog needed medical attention. I then decided I had to get him rehomed. Cooper is fine with other dogs when out walking. It seems to be a territory issue. His behaviour improves whilst I’m not around him. He has stayed at boarding kennels twice before and behaved very well apart from being anxious at the beginning of his stays. He is very friendly around adults and children that he knows. He lives with 2 cats and has shown no aggression towards them and sleeps with them on my bed. He is neutered and is up to date with his vaccinations. He has no other medical issues. He is KC registered.