Home DIY

I would like to install an outside tap. I bought a kit that self cuts into a cold feed without the need for turning off supply, apparently. Has anyone used these? will I be taking an inpromptu cold shower and fucking my plumbing?

Or would t-ing off the washing machine supply be a better idea? Threaded connection with PTFE tap (20 wraps, obvs) instead of piercing a copper pipe with blind faith.

I'll just need to find the right connector. Can't quite picture the current run, even though I only replaced the kitchen tap a month ago.