In reply to abr1966:
Under criminal law the owner and anyone in receipt of rent will have legal responsibilities.
The house must really be in a very sorry state if its uninhabitable and require 6-8 weeks to get into a liveable condition. I presume it was liveable before the xmas period, for it to have fallen into such a condition so quickly seems a bit odd. Pest proofing works are not usually that onerous. The agent or owner should have employed a pest control contractor and I'd be wanting to see the report. Whilst this may not be what they want, the students have every right to live in the house and the owner/agent should ensure the house is fit for human habitation.
Consider contacting the Environmental Health team at the local council. They can carry out a survey of the house to look for hazards and have a number of powers they can use to require the owner sorts out any defects that are causing hazards. The council may also employ officers who can give advice on tenancies and the rights of the students.
Landlords and letting agents have an increasing number of legal obligations: right to rent checks, security of deposits, electrical safety etc. There are a number of options for applying some pressure if needs be. Is the house a house in multiple occupation? Should it have a licence? Occupiers can claim rent back if they lived in a house that needed a licence but didn't have one.
https://england.shelter.org.uk/professional_resources/legal/housing_conditi...
I'd expect the agent and owner to compensate the students for the condition of the house. If not the students could also apply to get compensation if the house is not fit for human habitation:
https://www.gov.uk/government/publications/homes-fitness-for-human-habitati...