Unless an employee can show that he is genuinely required to live in accommodation provided for him in order to do his job properly, the value of the accommodation and costs associated with it will normally be treated as taxable "perks".
There is a useful free "Living accommodation benefits in kind calculator from Digita Tax Central on the TaxCentral website.
HMRC Guidance Notes EIM11501 "Living accommodation: part of premises used for business purposes: overview is a good starting point for dealing with tax question arising from business use of living accommodation.
See also notes at Accommodation provided by employer/security of tenure position