Correx is known as lots of things, corrugate plastic, corotherm, coroplast, it depends on the brand but yes all the same thing, you need it at about 4mm thickness ideally.
B&Q do stock it although it’s often cheaper if you just go into local sign makers shops, or some people even recycle old for sale boards from estate agencies etc.
I personally really like having a loft. It means i can keep the food separate from their play area so i have their hay rack, nuggets and water bottle up there. Don’t forget if you have an upper level to include enough grids for a floor as well, as obviously on an upper level it will need something to keep the base (correx) up.
For my ramp, i bought some square guttering and lined it with a carpet floor tile from B&Q, just hot glued it on and then drilled two holes in the top and attached it with cable ties. Lots of people reinforce the cubes and little clips that come with them with extra cable ties just to keep it secure. I personally just use cable ties and no clips.
So with 26 grids you could have at max a 10x3 or 11x2 with no upper level. Or something like an 7x2 with a 1x2 loft depending on the shape you want. I don’t think you’d have enough grids for a 8x2 with 1x2 loft.
It’s often good to look at what other people have made to get some ideas on what you want. So heres an example of my cage. It’s 2 cages combined for 3 pigs in total.
It comprises of on the lowest floor, a 2x2 for one piggy, then bedside him a range of storage for all my piggy things, above that there is the main 2x4 cage for my 2 boys, that also has a 1x2 loft with my gutter ramp. This took a lot of grids as you can imagine as i chose to make my stand out of grids.
I think in total there is 46 grids roughly, and that involved buying two packs from Amazon.
Like you said you can expand all the time, my first cage was just the 2x4 with 1x2 loft and stand i’ve only recently added the 2x2 cage for my loan piggy. The best thing to do is look at the space you have and just draw different designs that would fit that area, taking ideas from things you like about other peoples cages. Hope that helps.
Although be aware the yellow base just sits inside the grid frame and has nothing attaching it to the grids.
