Decorating a bathroom help

[m0t]

The next project in my new extension is to decorate the bathroom. Currently the room is bare plaster with 18mm plywood floors. Lighting and ventilation are done. All the pipes are in the right place in the walls/floors. We want a karndean floor (or similar) which has to be laid on 6mm plywood so I have some questions about that as well.

Is this the right order to attempt this?

1. Bring pipes out of walls and cap.
2. Bring waste pipes through floor.
3. Lay 6mm plywood to top of existing floor. I was going to run under the bath. Should I run under the shower tray too? I thought butting up would help lower the tray slightly.
4. Tank shower area.
5. Fit shower tray and bath.
6. Fit floor. I know this needs to go under the bottom row of tiles but should I fit before all the tiling or tile the room down to the last row and then fit? I've seen people online batten the walls to allow them to do this. I know this goes under the toilet and basin but should the bath also sit on top or not?
7. Tile walls
8. Paint ceiling
9. Fit shower and enclosure
10. Install toilet
11. Install basin
12. Install towel rail
13. Anything else?
14. Drink beer.

Thanks for any advice