You may need to get a certificate to show that your property is fit for habitation. Certain properties don't need to get the certificate, but it is an offence to fail to apply for one if your property isn't exempt.
All rented properties must, at the very least, meet the basic fitness standard. However, even if your home meets the fitness standard it could still be regarded as unfit by inspectors from your local council. You should try to maintain the property to a standard that you would be happy to live in.
The Rent Officer, rather than individual landlords, sets all rents for protected tenancies. If a landlord wishes to increase the amount of rent which can be legally charged on this type of tenancy, s/he must request a Rent Determination from the Rent Officer.
You should give your landlord a reasonable amount of time to carry out repairs. If you are having difficulty contacting your landlord or your landlord has refused to carry out essential repairs you may be able to get help from your local council.