I suspect you need proper legal advice.
At the point when the business tenancy ran out, you could have applied to a court to have it renewed, if the landlord would not renew it. This statutory protection applies to most business tenancies and succeeds unless the tenant has breached his obligations under the tenancy.
Unfortunately you did not do this, and a tenancy at will was created.
Business tenants have no such rights under this type of tenancy, so you need proper advice to see if you can claw any of what you appear to have lost back again.