The notion that the LL must give 24 hours access BUT is over ridden by "quiet enjoyment" is an odd one. This is copied from HM Governments website as a typical model contract so one would assume HM gov have got it right.
Here it is in case anyone is interested.
www.gov.uk/government/publications/model-agreement-for-a-shorthold-assured-tenancy
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6 ACCESS TO THE PROPERTY BY LANDLORD OR AGENT
Routine access
6.1Provided the Landlord has given the Tenant at least 24 hours’ prior notice in writing, the Tenant must give the Landlord (or any person acting on behalf of the Landlord) access to the Property at reasonable times of day for the following purposes:
(a)to inspect its condition and state of repair;
(b)to carry out the Landlord’s repairing obligations and other obligations under this agreement; and
(c)to carry out any inspections required by law including (but not limited to) gas safety inspections, fire safety inspections and inspections of any smoke or carbon monoxide alarms installed in the Property and to carry out any works, repairs, maintenance or installations (including the installation of any smoke or carbon monoxide alarm) required by law.
Access for the purposes of selling or re-letting the property
6.2Provided the Landlord has given the Tenant at least 24 hours’ prior notice in writing, the Tenant must give the Landlord (or any person acting on behalf of the Landlord) access to the Property at reasonable times of day in the following circumstances for the purposes specified:
(a)where the Tenant has given notice under clause F2 (Tenant’s rolling 3 month break clause), to show prospective tenants or purchasers, letting agents or estate agents around the Property, but only during the last 3 months of the Tenancy;
(b)where the Landlord has served a notice on the Tenant under clause F3 stating his intention to sell the property, to show estate agents or prospective purchasers around the Property; and
(c)during the last month of the Tenancy, for any of the purposes mentioned in paragraph (a) above.