When you sign a tenancy agreement, it should be stated in it who is responsible for the end of tenancy cleaning at the end of the tenancy. Usually this is the tenant however, in some circumstances the landlord will be the one to do the cleaning. In case it is the tenant, then the end of tenancy cleaning has to be performed in such a way that the landlord is happy with, in order to return the security deposit taken at the beginning of the rent.
Landlords are very picky when it comes to end of tenancy cleaning. They will make your move out very stressful with their long checklist that they use to make sure that you have been a good tenant and deserve every penny from your deposit. If you want to make sure that will happen, then hire professional help. There is no need to exhaust yourself with the cleaning as you may not even be able to do it well enough. Professional cleaners know how to tackle the property and clean it in such a way that it passes the inspection.
End of tenancy cleaning usually costs somewhere between 84-220 GBP depending on the size of the property. Yes, it is pricey however, remember that if your landlord has to charge you for it, they will most likely take a lot more from your deposit. Remember to carefully read the tenancy agreement in order to know who is responsible for the end of tenancy cleaning and if you can, get yourself out of it.