I need to quickly modify the stock levels and prices etc from admin.
 
How can I show all items for sale in tabular form, so I can edit each parameter/variable quickly.

Select the category, go to the products opposite and check those you want to edit - click "Edit Selected" and you get a list of fields - you can select just stock levels and prices and edit all in one page view.

Yes thats good and it works and it remembers the fields selected.
 
But what about all products ?? not just in one category