my challenge is, before the plumber comes back to fit 2 x 'fast fix' brackets and a bar valve, to fill up the channel in the wall with something that will take plugs and screws to fix the 2 x brackets. I could put mortar in the channels but the word is that it is bad form to have copper pipes running through cement. What is the 'professional' way of filling the hole before covering the wall in acrylic sheet.
