My friend got a new fridge with a chilled water dispenser and ice machine and asked me to hook it up for him. Seeing as on the other side of the wall is the toilet I just drilled through the wall and teed into the feed to the cistern. I don't see the big deal but I'm coping some flak over it.

Very funny, btw. You're up for a jerry-rig award.
It's bright blue 1/4 poly pipe so it's pretty conspicuous when you go into the toilet.
People are like Wtf, oh shit, ugh yuk!