We went to our local flooring shop and bought a vinyl off-cut for £10. This has covered the two levels of the cage and there's enough left to cover the floor of their travel cage. The only problem with the vinyl is that our guys don't use litter trays, so we needed something to absorb liquid and keep the corner of the cage that they toilet in clean.
I ordered a bumper pack of Pampers bed mats, designed for children that wet the bed which is a much cheaper option than using puppy pads. They are absolutely gigantic as you can imagine so I cut them in quarters and change them twice a day. There are seven pads in one pack and the box I bought contained four packs. I use double sided tape to secure them to the cage floor, which works to a certain extent; it depends how naughty the ferrets are feeling, they can sometimes pull the pad up from the floor and then leave it in a crumpled heap! But all in all this is a much better arrangement-no more tissue everywhere!
The water resistant underside features an adorable teddy bear design, for what purpose I'm not entirely sure but it's cute in any case. As you can see from the pictures below the topside is a soft porous membrane over the top of a cotton wool like material. It has large wings consisting of the top layer of material for fixing to a bed, I use these as extra cover for the cage.
Here's the finished result on the top level :)