Leaking Pipe Ruins Expensive Bespoke Kitchen! 

I'm not a plumber but I've done plenty of copper soldered joints, I don't think that it would be a problem to use sandpaper to clean the pipe. I think the key thing is all the oxidisation is removed ready for flux, the solder will fill any gaps or lack of smoothness, just as it fills the gap between a cut 15mm pipe and an end feed fitting (I find that a cut 15mm pipe is narrower than the uncut end when using a pipeslicer)

My report would have recommended to replace all pipework in screed.. 1 pinhole will lead to another.

Pressfit 🤓