Thoughts and Advice on leaking bathroom

Hye guys, I live in far North Queensland, Australia, Im in a very old Queenslander style house, its falling apart and we have a deal with the agent that we dont ask for anything to be repaired and we keep our ultra low rent. The house has a lot of problems but one is becoming quite bad. Attached are some photos on the 2nd bathroom. it has two big problems. The first is that we have some sort of leak that causes water to seep out the bottom of a small partition wall at the end of the bath and flood over the floor. The second is recently we have had a drop in pressure from the shower itself. We are looking at trying to fix the problems in one big go. The wall that all the taps are set in is solid concrete, the little partition wall is breeze blocks. We are thinking of pulling off the tiles on the shower wall, my housemate believe the piping will be set into the wall and covered over, so we will have to chip it out. Once we have it all exposed we want to get a pro in to replace the pipework. Then we can re plaster and re tile after he is done. What i wanted to find out is whether you think the pipes will be set into the concrete or just in a channel. How much piping do you think would need replacing looking at the fittings? Time to fit? Looking at where the leak is at the foot of the bath unit, do you agree that it could be the pipes leaking and running along the inside of the walls or does its location suggest something else leaking?