The fact that your landlord may have broken the terms of your lease will probably not entitle you to bring the lease to an end. Nevertheless you may be able to take legal action against him for any losses that you have suffered as a result. If the breach is ongoing you may be able to apply to Court for an order that your landlord complies with his obligations.
Alternatively, you may be able to use the landlord's failings as a factor in your negotiations to bring the lease to an end. In practice it is usually better and cheaper to negotiate a solution than to take Court proceedings.
