Excuse me, and forgive me if you've already answered this question, but where do you go to download the base files? I'd really love to colour these but I cannot find an actual downloadable file.

Those are bases - they are not templates with layers and Furvilla won't provide those (because their artist basically does everything on bases as well).
To color it, click "Full View" and just save the image.
Then, open the link from the description - it's the tutorial made by the Furvilla artist on how to color such greyscale single-layer bases.

I'm not in any way associated with Furvilla nor I'm a good artist myself (but love color-ins), but if you need further advice, just ask - I've already experimented with those bases. ^^

;A; amazing! But still no chinchilla >v>

Nor a mouse! S'blasphemy. Adorable blasphemy!

Yes, we need mice too! ;A; <3 The rodent population must grow!

I love the art style!

http://www.furaffinity.net/view/22114522/