We have been playing around with this today and this is the layout we think we will go with. Due to solid floors and walls if we move the loo we need significant boxing in. My app has limited selections of items but we will have sanitary ware in these locations, we think!

Generally a larger tile will make a room look bigger than a smaller one as they are less 'busy' also go for lighter colours across all surfaces (ceiling, floor and wall) if you can to increase the light in the room. If a Building Inspector is involved you may need to keep a certain colour difference between surfaces, but in the past we have negotiated a band at skirting level and at the edge of the ceiling to satisfy the regulations which could be an option if needed. The old idea of using mirrors to open up a space really does work. I don't know if you will have a window - if so I assume from the description that it would be either a velux type roof window or a vertical dormer window - either way if you have one try and put a mirror opposite if possible so the room is opened up even further and the light bouncing around the space is amplified. I know Ideal Standard do 'Concept Space' fittings that are more compact than their traditional counterparts which might be worth a gander. You can also get WCs with a sink over the cistern, an though these have never personally appealed, sometimes a small space breeds necessity. Good Luck!

Thanks all this is very reassuring! Here is a pic of the layout. The wall between the bedroom and the en-suite is going to be stud while The opposite wall with sink against it is a solid outer wall (but we’ve an extension the other side of it now) so that was making me think if I put the shower head on that wall then I’d need to have it built out a bit to accommodate piping Or chased in (?) - so perhaps the more logical option is to have the shower head on the bedroom wall side where it’s stud or from the Far end wall and then Pop a niche in the stud? Wet room would be the dream Sarah but I think too costly for us so hoping we can get a slimline tray not on risers ideally, or if it has to be raised, to make a feature of it by tiling or making a wee flat bit before tray starts.

Is tanking the space to make a wetroom an option? Anything that reduces the visual separation of the shower will help the space feel larger - alternative to wetroom is matching the colour of the shower tray to the flooring. From a useability point of view, turning the loo 90 degrees so the same bit of floor is used for the space in front of the loo, standing at the sink and drying after the shower may help. Means careful selection of fittings - short projection loo and sink - but there's loads of choice out there. If you go for a vanity unit, drawers are easier to access in a small space than a cupboard (and there are wall hanging ones if you want to keep more floor clear to increase the feeling of space). Even if you can't use the (excellent imo) suggestions to steal a bit more space by working the entrance in with fitted wardrobes, I think you've got enough room for an ensuite. Good luck!