I'll copy and paste this message here that Platty sent me about bestas. I don't think he'll mind. A good bit of info here.
Basically you buy a bog standard besta bookcase (single or double):
https://www.ikea.com/gb/en/catalog/products/40102129/?query=401.021.29
Then you can Choose what doors, feet, handles and there is also a mirror back / glass shelf insert you can buy for quite cheap.
(The feet and handles aren't absolutely necessary mate they come with it. Really you only need the bookcase and 3 doors.)
Also there is a few lighting options, these look great and were made especially for besta, and you can see them in the video:
https://www.ikea.com/gb/en/catalog/products/50165404/
Here is the glass shelf / mirror back insert you can use in bestas:
https://www.ikea.com/gb/en/catalog/products/50196542/
My doors:
https://www.ikea.com/gb/en/catalog/products/40103553/
Voorhess doors (I think)
https://www.ikea.com/gb/en/catalog/products/70178580/
Another set of doors but not great if you want to see what's in there:
https://www.ikea.com/gb/en/catalog/products/50227280/#/50178492
A better view:
https://www.ikea.com/gb/en/catalog/products/S99895383/
So when I was finished I had this:
https://www.ikea.com/gb/en/catalog/products/S49887677/
Here is a good video showing exactly what I have (minus the lights) The aluminium doors look great imo.
https://www.youtube.com/watch?v=y9Wx5UO59LA&feature=related
I've bought 2 of the cabinets found at the last ikea link.