Hi all thank you for your comments, the bathroom is 2700 wide (window wall) and 1800 deep- looking at 2D plan from doorway, less the boxed in area to the left of the window which is 700 x 800 which creates the fixing wall for the shower head, and and an alcove for the basin area. As you can see it is a planning nightmare and all your suggestions are very useful, I had thought of closing in the window all together & putting in a skylight, but externally it would mess up the appearance of the upstairs windows that are all the same and look nice from the street view.Always a balance between one decision and another. All other options for placing the shower = claustrophobia and given the room is already so poky, at least a shower floor area of 1370 x 800 will give some sense of space. Ive read up on so many design ideas for small areas, thank you angelasusanm, I'm shuffling papers all over the place as I love proportion and a bathroom with many angles is difficult, especially for tiles to look good. This bathroom is not a redo - its never been completed and so there are no skirtings or wall tiles or anything, the pic has a piece of wood looking lino on the floor.

you may like to consider powder coated steel coving for skirting boards in your bathroom...should be available at any tile store and colour choice is very personal but same colour as floor can look more spacious

Two options for your floor For a Quality Bathroom Renovation 1) Best Option Remove existing yellow tongue, the sheets may extend be under the walls to the adjoining room, can be done...NOT an easy job, hand saw and chisel 2( Hardies Ceramic Tile underlay nailed onto the existing yellow tongue, MUST be nailed to manufacturers specifications. Nails, as specified and spacing as specified. 3) Walls ...Plumb Studs, add noggins for vanity, recessed shaving cabinet et all check top and bottom plates 4) Rough In Plumbing 5) 6) Rough In electrical 7) Insulate walls with Sound Check Insulation,,, Add flashing angles in corners... 8) Fix Hardiflex to specifications 300mm centers, galvanized clouts if using wall tiles up to 15 mm use 6.5 thick villaboard, if over, use 9 mm villoaboard 9) Sikaflex with 11FC all gaps villaboard to floor, 10) Waterproof , apply ( Davco K10 plus, easy one to apply. not toxic nor inflamable whole floor, showed say 300 above shower screen 1 metre to sides of the shower, 600 above bath, vanity, 400 around remaining bathroom walls 11) Shower wall to floor, and about 300 past shower, add Polyester Bandage abt 100 mm wide 12) Fix water bars to, shower and door ( MUST be level ) with Sikaflex 11 FC 13) Second coat of waterproofing to all areas 14 ) Tiler to "top floor"/ lay tile bed, 15) After drying 4/5 days, WATERPROOF on top of tile bed, with another Polyester Bandage in shower area....the waterproof on top of the tile bed is to keep the tile bed dry .. two coats in shower 16) Commence tiling

how old is the house as you may need to check for asbestos on walls and floor and is teh whole house a slab on ground if not the floor under the tiles may not be concrete..., when replacing floor tiles i would also replace skirts to ensure waterproofing is above the floor all around (and avoid a potential leak at the join) and depending on what you are planning to do (ëg install new shower stall or wet floor?) i would also consult your tiler about "levelling the floor" which is much more complicated than we think.. and take your time removing the old tiles, especially on the walls as it's better to do as little damage (to the structure and yourself) as possible and you will find many online DIY instructions for retiling that are worth reading before you start...good luck with your project