Good Lawyer Guide's response

In general terms, the landlord is responsible for the actual physical structure of the flat and the exterior of the property including gutters, pipes and so on. The landlord must keep all service installations in full working order and must ensure the safety of items such as gas and electricity, and the flat’s general fitness for habitation.

As the tenant, you must report any issues of disrepair to the landlord straightaway so that the landlord can fulfil his obligations. You have a responsibility to keep the interior in a good state of repair and to look after it in a reasonable way. This means, for example, you should clean the windows, unblock sinks and not allow anyone to damage the property. If you fail to fulfil your obligations the deposit you paid at the outset of the tenancy could be at risk.