There are no implications on the land title at the LR unless you are splitting the existing plot as recorded by the LR. Change of Use is definitely nothing to do with the LR (sorry Ethel).
Change of Use requires a Planning Application to the local council (in every case - I can think of no exceptions to this).
If you have been using it for storage for 5 years, and DEFINITELY if you are renting it commercially, you may already be in breach of the existing planning - which will be for agricultural use (as in pigs).
However this doesn't matter as the worst that can happen is that you are asked to cease doing this - via a Statutory Notice if necessary. You would be gain any PERMANENT entitlement to use it for storage until 10 YEARS have passed.
However none of this matters if you are wanting to use it for farm-workers now. You will have to apply to the authority with a Planning Application. If you can show that there is a need for such accommodation, you will normally be granted it - either temporarily for up to 2 years (as in what happens when a farmewr erects a caravan for such purpose) or permanently - but be aware that an Agricutural tie will be put on the planning consent. This means that you can only use it for agricultural workers. This constraint is the way the planning authorities prevent despoiling the countryside with new domestic dwellings - where the policy in most parts of England & Wales is that it is against policy to construct new dwellings in the countryside.