Graham,
The PQ will be exactly the same as you get now,and you wont get Sky One.
An FSFS card just gives you access to the handful of FTV (Free to View) channels. FTV channels,are as follows...
Five,Fiver,Five USA,Fiver+1,Five USA+1,Sky 3,Viva, 4HD and a few extra shopping and chat line channels, plus 5 HD when it launches.
Though if you're getting a FSFS card because you're considering cancelling your Sky sub then you don't need one- Your current subscription card will give you access to the FTV channels even after you cancel your subs...
You will also have access to 250-ish FTA (Free to Air) channels,but you dont need any viewing card for those as the are broadcast completely un-encrypted.
Full list of FTA channels is
HERE.