Welcome to the Forum.
I am sure you will get lots of great advice on here, and there are many people using C&C cages with fleece or vet bed.
The best place to start would probably be the C&C thread in hosing.
I got loads of great idea from looking at how everyone else had arranged their cages on there.
Member Gallery: C&C cages/homemade cages
My advice would be to plan on the guinea pigs not using the loft immediately, so I always makes sure I have at least a couple of food bowls and water bottles on each level.
And I also use large, high sided trays with hay in them. This helps reduce the amount of hay that gets tracked everywhere, as well as serving as a toilet area. I line the trays with newspaper and change them completely at least once a day. In addition ot the two hay trays I also have several hay bags with smaller amounts of their special hay in (just a different hay from the main one!).