Well, I think that may solve the problem, but brings up two others. I had the catalog displaying three columns per row and after merging everything, it is a single row. I'm pretty sure that is because I had another module installed that allowed column display but forgot about it.
The part that I have to ask about is in the instructions:
Please note that you still need to assign special privileges to certain customers you want to allow access to products of categeories / manufacturers you configured in points 2. and 3. in this segment.

To grant access to these customers go to Admin > Customers > Customers and individually open the details of your chosen/approved customers.

In your list of customers you will see a new column on the right hand side headed Privileges. By default the icon is a red cross. You can sort this column to find which customers are 'privileged' or not.

Near the top of each customer's personal details you find a dropdown called Customers Special Privileges Status. The default is 'None'. Set this to 'Has Special Privileges'.

Update the customer file - done

The icon in the customer listing is now changed from a red cross to green indicating that the customer has special privileges.
As I understand it, I would have to go and update all 1,600 customers individually to access the logged in products?
Can you tell me what file to edit to default it to "'Has Special Privileges" rather than "none" or am I mis-understanding this?
Thanks