FITTING A MIXER SHOWER NEED ADVICE!!!

[bonnessbenjamin]

Hi guys, im after some advice! I recently bought a triton sema mixer shower. So far I have knocked down the plasterboard from my breezeblock, which is behind the bath, so that I can install the required copper pipe to give the shower water.

My questions are as follows:-

1) Should I have made two 3" deep channels in the breezeblock to house the new piping? Iam just worried this may have affected the integrity of the wall.

2) I have 2 tanks in the house. One that heats up my water in an airing cupboard and one in the loft that i assume keeps cold water in. Should I simply just attatch two more pipes from the ones that are giving the bath its water OR should I run the hot from the bath and the cold from the tank in the loft?

I know its long winded but I have never installed anything like this before, hope you can help MANY THANKS...!!