Nintendo UK has started emailing customers to let them know that issues that arose with regards to the Build your amiibo Bundle has now been resolved and that items should now be going through as normal. Here’s what they had to say about the issue on the Nintendo UK Store.
Dear Nintendo fan
We apologise, we have experienced some technical issues with Build Your amiibo Bundle for New Nintendo 3DS, New Nintendo 3DS XL and Wii U over the last few days. These issues have now been resolved.
Kind Regards
Nintendo Official UK Store
Source: Email

I didn’t know they were even having problems.
Neither did I.
What exactly is the Build Your Amiibo Bundle?
What the hell, UK!? Is there any video game retailer NOT having issues with their systems in your country!? First GAME & now we hear about this! Well least Nintendo UK fixed the issue before it got as bad as GAME’s.
Yeah I tried to order just for fun, you know, build the bundle and then just exit the webpage. It wasn’t working, when you tried to select an Amiibo it went to the Amiibo advertisment page instead of just selecting the dang thing.