Turn the toilet round - the waste pipe can go out sideways and be boxed in. Build a partition wall (shown in red above) so you have enough space to put a shower against it (the shower shown above is 1100mm x 800mm). Or, if you don't want to lose the light from the window make the new wall half wall half glass (as in this picture), or all glass, and have a custom made shower enclosure. There should be enough space to fit in a basin so the door will still open. Good luck with your project!

I've been thinking about options to cover all basis and came up with this. To allow guests to use a bath/shower the ensuite would be shared. I added a wall in the master bedroom to divide it and add privacy so guests don't have to walk into the bedroom to get to the bath/shower. The upsides are that the ensuite is larger, includes a bath and shower and has more vanity room. Also, by diving the bedroom I can add sort of a walk-in wardrobe. The downsides are that there's only one bath/shower that has to be shared and guests have to walk through the walk-in wardrobe to get to it. Also, it reduces the size of the master bedroom but it's quite a long room anyway and it would cut out the light from the windows in the bedroom. Personally I don't see these as big problems but I guess some people won't like it. Do you think this is a good idea?

Is there any room for stretch in the dimensions? I haven't found one that ticks all the boxes.. however as I suspect size is the more important factor... none have lights.. and some you'd need to add a separate shelf.. https://www.ikea.com/gb/en/p/enudden-mirror-white-50243162/ https://www.wilko.com/en-uk/alaska-1-door-white-mirrored-wall-cabinet/p/0463499 https://www.made.com/made-essentials-bex-oval-lacquered-mirror-60-x-40-cm-black  https://www.wayfair.co.uk/home-decor/pdp/borough-wharf-eruh-accent-mirror-jorg1193.html https://www.wayfair.co.uk/home-decor/pdp/mercury-row-parkersburg-mirror-box-kswk1078.html?piid=18983395 If you can stretch to 64cm tall... https://www.ikea.com/gb/en/p/silveran-mirror-with-shelf-white-30268002/ - I don't know if you could make this fit, if you could get an electrician to add a light like this one? https://www.wayfair.co.uk/home-decor/pdp/metro-lane-westman-bathroom-mirror-uzg2319.html  https://www.ikea.com/gb/en/p/lillangen-mirror-cabinet-with-1-door-white-80205168/

Hi Rhian Foley Having looked at your layout as you have sketched, a big bathroom is good as bathrooms and kitchens are the items that make a house. The only thing I would try to change is the en-suite in the master bedroom, possible long and thin if possible and along the party wall near the stair. Hope this helps. p.s. I almost bought a house with that layout and was thinking of doing a similar extension.