As Jonathan says, you start with the Soil pipe, and if you've agreed with your bathroom fitter that he's able to put the pipe across the wall behind the toilet and under the bath to get to the outside wall, then that's fine, but if not, you really need to discuss it with a professional. There are many reasons and regulations that you need to stick to with regards placement of soil pipes, because sometimes you need access to unblock them. When designing a bathroom, it is important to know where you have to have some items and then decide where you can put the other items that you want. Check the soil pipe situation as this dictates where everything else can go. I suspect unfortunately, that if you can't solve the soil pipe problem and the toilet needs to go on the outside wall ( which is the normal place for it ), then you may have to have a re-think and possibly change what you have purchased. I've tried to have a re-jig with what you've purchased and moving the toilet to it's normal position, but i can only make them fit if you do what Jonathan suggests. Even then, I would suggest that the door be moved along the wall to accommodate the tall unit. You will have pipework from the vanity that you need to box in, it can go under the bath, but at least it's just water not the soil pipe. I would have also considered a bath to fill the whole gap of 2000mm not a 1700mm, but you can use the gap to build a space at the end both covering the pipes and giving you somewhere to stand toiletries. The taps for the bath aren't marked, so i'd probably put them on the bottom end nearest the vanity on the flipped plan below.

your options? I guess they are 'macerator', boxing-in the soil pipe probably along the skirtings and then down in a corner, or - the best solution, but most involved - re-route an underground soil pipe to the existing drain so that you do have one on that side of the house. Going through joists with a soil pipe is expensive and not safe. So that is not an option. Core a hole through outside wall, fit new stack, & then connect into existing pipe run.📷 And by the way, there many out there who will say definitely avoid a macerator, nothing but trouble,especially if things are put in it which shouldn't be (that happens!), they block and then you have ''trouble'' everywhere. Heard stories of it coming up through a basin, bath & shower outlets, not pretty, even a basement ankle deep. Sorry for the picture, better to imagine it than to have it happen.

Can I ask why you are adverse to the corridor feel as you go into the room? Looking at your plans - the room opens up at back where the extension is, and I’m guessing with those lovely large windows at the end, this is where you would like your sleeping area?? If it is, it makes sense to have your bathroom and wardrobe at the door end. Think about standard hotel rooms - that’s kind of what they do to ensure a larger squarer sleeping area. The width of the room as you go in is around 2.8m - this area would feel cramped with a bed - however would work really well with the en-suite!

Hi I’m not sure if anyone can advise but I’ve had a leak coming into my kitchen, I’ve replaced all my guttering but it looks like one part of the guttering runs into my soil stack and I can see drops of water coming from the soil stack at certain connection points. Do I get a plumber or a drainage repair person? Thanks I’m clueless