Are there any industrial strenght finishes I can put on the boards?.
Someone
mentioned yacht varnish to me...

If you want a hard wearing surface and don't mind varnish, use a "diamond"
hard floor varnish. Dulux and Ronseal do versions. They are really very
expensive, but do work. You'll need to remove the existing finish first.
Don't even think about using anything other than "clear". Coloured varnish
looks awful.

Christian.