Hi Mike
Is the floor reclaimed or rough sawn?
This is important in the cleaning process required.
If it has definitely NOT been sealed use Lithofin Wexa in the general clean if it has been impregnated by stains then you can use a product called Lithofin Stainaway, you need to use industrial equipment to make a success of the job, IMO.
When done offer to protect the floor with Lithofin Stain-Stop as an extra this is recommended for maintenance and general every day cleaning.
Go to this excellent site Mike for the correct products and procedure it will guide through the correct cleaning method.
: www.extensive.co.uk
Good Luck