I thought I would spare you all my mistake!.
If your putting a shelf up above the sink in the upstairs bathroom DO NOT drill anywhere near the border tiles!
The pipe feed for the sink runs along behind it HORIZONTALLY not vertically!!!
So drop your brackets down below the border or put them well above it.
Needless to say for a few minutes my bathroom had two showers!,
Hopefully that will help any others from making the same mistake (I think I'm the second)
For all who ignore this warning Eroski do 15mm push fittings quite cheap!!!
Well, youve gottta laugh!
All the best folks!