Problem with Free Shipping by Category

[flyingbrick]

I have the following scenario I need to cater for:

 

A) In the shop I have created all tents go with free shipping.

 

B) All other goods are by weight and aligned to Royal Mail 1st Class

 

My expected outcomes are if a customer were to buy any tent their entire order will result in free shipping. All other orders without tents would result in a 'by weight' calculation for postage.

 

To do this I have enetered weights against all products and set a table rate for the weight bands.

 

I have also implemented Free Shipping by Category http://addons.oscommerce.com/info/4475 and attempted to select all the tent categories for 'free shipping'

 

But it doesn't work, and importantly once I have selected the categories for free shipping in the admin for the module they do not show when I save changes to the config.

 

And now I'm stuck.