Repairs: Who Is Responsible for What
The split is largely set by statute rather than by the tenancy agreement, which surprises landlords more often than tenants.

What the landlord cannot contract out of
Structure and exterior, and the installations for water, gas, electricity, sanitation, space heating and hot water. Those obligations are implied into almost every short residential tenancy and cannot be signed away, however the agreement is worded.
The government summary at gov.uk is the clearest short statement of the split and worth sending to a tenant who asks.
What sits with the tenant
Day-to-day upkeep: changing bulbs and smoke alarm batteries, keeping drains clear of what they put down them, minor gardening where the agreement says so, and reporting problems promptly. That last one matters legally - a small leak left unreported for months becomes partly the tenant's problem.
Response times, in practice
There is no single statutory clock, but the standard expectation is same-day for anything dangerous, a few days for loss of heating or hot water, and around two weeks for non-urgent work. Winter shortens all of it where heating is involved.
The practical advice is duller than the law: answer the message. Most disputes that end badly began with a repair report that went unacknowledged for a fortnight.

