Hello I am a solicitor with 20 years experience. I will try to help you with this.
Your landlord has a duty under S11 Landlord & Tenant Act 1985 to keep the structure and exterior of the property in repair. He is clearly in breach of this. He has a duty to repair the property and you will be able to claim compensation against him. The level of compensation will depend on the severity of the disrepair and how long he has been aware of the problems.
If your means are limited you may be able to get help from a housing solicitor through the legal aid scheme. Some solicitors are offering no win no fee for these cases. You will need expert help to bring the case. Follow this link to find a solicitor in your area who can help. http://solicitors.lawsociety.org.uk/.