While many overseas/migrant workers will arrange their own accommodation, there are some industries (for example agriculture) where the employer might provide accommodation.
If you are making available permanent, fixed accommodation (not temporary shelter) to workers, you should be aware this is subject to Housing Acts legislation enforced by Local Authorities. This does not apply to moveable accommodation such as caravans or containers.
If you provide residential accommodation in caravans, this is subject to the Caravan Sites and Control of Development Act 1960. Sites normally require planning permission and are subject to licensing by the local authority.