If you look at the Tier 4 legislation @Charlotte838 it says;
Staying away from home overnight
You cannot leave your home or the place where you are living for holidays or overnight stays unless you have a reasonable excuse for doing so. This means that holidays in the UK and abroad are not allowed.
This includes staying in a second home or caravan, if that is not your primary residence. This also includes staying with anyone who you don’t live with unless they’re in your support bubble.
You are allowed to stay overnight away from your home if you:
- are visiting your support bubble
- are unable to return to your main residence
- need accommodation while moving house
- need accommodation to attend a funeral or related commemorative event
- require accommodation for work purposes or to provide voluntary services
- are a child requiring accommodation for school or care
- are homeless, seeking asylum or a vulnerable person seeking refuge
- are an elite athlete or their support staff or parent, if the athlete is under 18 and it is necessary to be outside of the home for training or competition
If you are already on holiday in a Tier 4 area, you should return to your home as soon as practical.
Guest accommodation providers such as hotels, B&Bs and caravan parks may remain open for the specific reasons set out in law, including where guests are unable to return to their main residence, use that guest accommodation as their main residence, need accommodation while moving house, are self-isolating as required by law, or would otherwise be made homeless as a result of the accommodation closing. A full list of reasons can be found in the guidance on closing certain businesses and venues in England.
Accommodation providers are also encouraged to work cooperatively with local authorities to provide accommodation to vulnerable groups, including the homeless in Tier 4 areas.
So if the guest is moving to your area to look for permanent accommodation it sounds like they should be okay.
