Many of the members here have used mattress pads successfully with fleece. I looked in the beginning at lots of different 'piggie blankets' and fleece liners even here in the US but they were so expensive.
One thing I wanted to put in here is that while we love the designs and everything in creating a cage, our piggies don't care how perfect they are or how pretty they turn out :-). They only care that they are comfortable. Have fun with creating and what can be easiest for cleaning but do what's best for you and your needs. These things can become very expensive if you go beyond watching for clearance and sale fabric, etc. I used puppy pads for quite awhile under just a bunch of out of season fleece blankets I picked up for about $2. It was simple but effective and did the job.
I haven't found yet the liners we use a lot here as pads but have seen many people in the UK simply add the mattress pads. Congrats on the new cage-would love to see pics of the babies enjoying it when you are ready! There can be others there in your area that can maybe help out with other ideas but these are the ones I've seen on this forum thus far.
