If you stay past the end of your tenancy due to self-isolation, your landlord is able to charge for any losses they may incur. However, landlords during this period are being asked to be reasonable, and this has been communicated to all landlords that are members of the Unipol code.
By this we mean that the landlord should not be charging for anything other than a reasonable and evidenced amount that they have lost. This could be your rent (daily) or the actual cost of providing alternative accommodation if they need to for their new tenants. The university can provide emergency accommodation for students unable to move in, and at a reasonable cost that is likely cheaper than a hotel, you could ask your landlord to refer incoming students here to reduce the charges to you - https://www.unipol.org.uk/advice/students/coronavirus-advice-for-students-and-landlords#Moving%20in%20and%20out%20of%20properties.
Your landlord cannot charge for additional cleaning as they should be cleaning the tenancy to a Covid-19 safe standard irrespective of whether current tenants have or have previously had Covid-19.
If you feel the charges issued are unreasonable, we advise that you write to your landlord letting them know, stating how long you need to stay in the property and that you are only willing to pay reasonably evidenced charges. If they are a member of the Unipol code, you could also raise a complaint with Unipol. If they are not and you have difficulties after writing to them, please let us know so that we can advise further.
The legal position of additional charges are as follows.
If you have been given a notice to end the tenancy (a section 21 notice - https://england.shelter.org.uk/housing_advice/eviction/section_21_eviction) and you do not move out on the specified dates the landlord can charge you any costs they incur from your not moving. This could be the cost of providing accommodation to new tenants who cannot move in, or the daily rent until you move. The daily rent can be that for the full house, even if only one person is remaining there. They may instigate legal action to remove you and you can be charged these costs too.
If you have not been served a section 21 notice to end the tenancy, it is likely that the tenancy will naturally become a rolling monthly tenancy and you will be charged by the month (for the full house if applicable) until you give one months’ notice and leave.
Your landlord cannot evict you if you do not pay – if you cannot leave you do not have to until a court orders you to leave. The landlord may deduct the additional charges from the tenancy deposit, or seek this legally if it is not paid, but we anticipate they would struggle to make a legal case for anything more than direct losses given the current pandemic.