Your first step should be to get a copy of your rental agreement and read it again. If you can’t find your agreement then you need to ask your landlord or agent for a copy. Pull out the clauses that you think your landlord has broken and begin to write your e-mail/letter to them. This will inform them of what terms they have breached and gives them notice to rectify them.
You should include:
The property address
Today's date (ie the date of writing the letter)
The clauses you believe have been broken
The date of which you would like this rectified
If the repairs aren't done, you can do the repairs yourself (ie by getting a certified repairman or contractor) and then claiming back the costs from the landlord. You should keep all correspondence and receipts, including invoices. This will be important when providing evidence.
You can also contact the environmental health department at your Local Council for help. They must take action if they think the problems could harm you or cause a nuisance to others.
If your house isn't fit to livein and you think your home’s unsafe, contact the housing department at your Local Council. They’ll do a Housing Health and Safety Rating System (HHSRS) assessment and must take action if they think your home has serious health and safety hazards.
If these options don't work then you will need to go to court and get a court order forcing the landlord to repair the property. To obtain an order for specific performance a tenant will need to convince the court as to the urgency of the works and that any alternative remedies are inadequate.