Grouped Lettings

Tenancy Types and Management

I currently have 4 flats in one block. 3 out of 4 of the flats currently have Company lets with the same company. the 4th flat has come available, and this company want it and i would like to let them all on a company let as one grouped agreement so that the company is responsible for all the communal areas, the repairs within the building. Do you know how i would go about doing this? what agreement could i use? would it cause me any problems to do this? is it even possible to do it? would it effect insurance or refinancing or mortgage?