I have a very small bathroom which only has a shower and washbasin. I want to remove the shower cubicle and replace it with a bath and a overhead shower. Roughly what should that cost if I supply the new bath. So just the removing and fitting would have to be done.
I'd love to help, but I'm afraid this kind of job really has to be looked at to price properly. There are far too many unknowns for a "ball park" figure.
Pick likely suspects that you would like to do the job, and ask for quotes. It's the only way.