It will of course depend on what is needed to be done, but here is a general guide. Always put your repair requests in writing for evidence.
Priority One: Emergency Repairs - initial response from the landlord within 24 hours
This is any repairs that could be a risk to your health and safety or impact your immediate safe access to your house. Examples are carbon monoxide poisoning concerns, fire alarms not working, flooding, insecure external doors or windows.
Priority Two: Urgent Repairs - an initial response and inspection within 5 days.
This would cover anything that affects your day to day use of the house and affect the comfort or convenience. For example: toilets/showers not working properly, leaking roofs, minor mice infestation, problems with heating (unless in the middle of very cold weather then this may be more of an emergency where alternative heating should be provided).
Priority Three: Non Urgent Day To Day Repairs - within 28 days
These would be repairs that are affecting the standard of the property but not having an immediate detrimental impact on the household e.g. leaking gutters.