You don’t have to buy fleece liners. You can buy fairly cheap fleece blankets from B&M - two for £4.99, put towels and/or puppy pads underneath to soak up pee (don’t forget to prepare your fleece so that it wicks moisture away). Mine also have home made pads under houses/tunnels and around high usage areas. These get changed every three days. I use a large gravel tray with a puppy pad then a layer of shavings or Aubiose on top, then lots of hay where they can burrow, forage, pee and poop too! It’s almost like potty training them! This gets cleaned out every three days too, and I do a full cage clear out once a week. I poo pick every day - sorry that’s a horsey term but it’s the same thing - clearing the poop up out of their cage! It brushes up nicely with a rubber hand brush and dustpan £2.49 from B&M too. I’m sure your piggies will enjoy their new cage whatever you decide to do!