Large bath water jets & oxi shower diverter mixer fitted in tiled bathroom change to!

1/ Fit combisave to combi boiler in loft.
2/ Lot smaller bath,
3/ hot&cold taps fitted to bath
4/ item 3 above supplied before pressure equalising valve supplying shower oxi diverter mixer made by GREENS INDUSTRIES LTD,
5/isolate bath supply side of oxi diverter mixer hopefully leaving shower only to work?
6/ taps to supply bath water
7/hot tap to draw through combisave to enable oxi diverter mixer pullout knob to work?
8/ Tiling must remain intact
9/ all the above fitted 2004 prior to water meter being fitted. Combi in loft bad news for my water supply. Bath very slow to fill, unforeseen at time like to make quicker.