Advice required on new bathroom fitting

[cooa99]

Hi all, I am in need of some advice with my diy bathroom project. I would have happily given the work to someone else to do but labour quotes are comming in at about £4.5k minimum with 2 weeks completion time. I may not agree with the price but the period of work is just too long and I can only imagine thats to justify the labour cost.

Anyhow I thought I might as well start myself taking the floor tiles and everything else off in there. My task is to do as much as I can so that all that will be left is to
someone in to do the tiling. All plumbing work are exactly the same except for installing a thermostatic shower on the wall

Attached are some pictures.

Yellow line in picture (side-1) will be the height of the new tiles. The bath area will have tiles going all the way up to ceiling instead

Questions

1) Walls
My plan is to (use stanley knife and) cut off the plasterboard at the height of the current tiles rather than wasting time to chisel the existing tiles off. New plasterboard will then be inserted into place and the gap sealed. The bath area can be fully replaced (i.e. bath to ceiling) since that section has to be mositure resistant.

Any issues with this approach of only replacing sections of existing plasterboard (of non wet area sections) or do I have to do a a full floor to ceiling replacement?
Should I use hardiebacker board for the walls?

If durring I decide that all wall should be tiled, would there be any issue tiling on existing painted walls?.

2) Floor
Current floor is a chipboard with very minimal flex.I have taken off most of the tiles off it and it still looks ok. what should I use for the floor.
Hardiebacker or NoMorePly or ditra matting ?

3) Tiles
I plan on using large tiles for the floor i.e 600x600 to minimise grout line. Would same size be good on the wall as well or I should use 600x300?

Thanks

 

[Baths'N'Gas]

Nothing wrong with that time scale of 2 weeks.

What time scale was you thinking

 

[cooa99]

I was thinking more like 6 days. A friend had a slighly bigger sized bathroom done many years back. I should have done the bathroom then when same chap quoted me £1800 labour.

The timescale would mean us having to get a hotel which ramps up the overall cost a fair bit.

Ideally I would like to take on the work. I could do with the mind, body and soul excercise. I could always get the pros in if I am knakered from stripping th room bare. Surely that cuts down the labour cost a bit