It all depends on the layout of the shower you are replacing. Is the wall tiled behind the shower ? not always, this may involve additional tiling or a shower with a larger footprint. There is no magic one shower will fit all.
The Triton T80Z is recommended as a replacement for all previous models of Triton T80, T80Mk3 , T80i, T80si and T80xr.
The T80Z is also an ideal replacement for other makes and models as water and cable entry points can be connected to the left and right hand side of the unit.
The Mira jump specifically designed for replacement of right hand side water inlet electric showers, Retrofits Triton, Aqualisa and many other electric showers
The New Bristan range also has multiple cable and water inlet configurations and was designed as a replacement shower, and is available in four models.
All these showers have a good lay out for retrofits, with more flexibility in both the pipe inlet and electrical connections. And a decent footprint to cover existing holes in your wall.
There is no magic one shower will fit all.
Remember we can supply and fit a suitable shower, or alter your services to suit, if you want a particular model of shower.