Consider losing the bath and providing mitred shower tray to tuck against angled wall. Adjust stud work around shower if necessary to do this. Provide back to wall toilet with concealed cistern. locate flush buttons behind slow close seat and then the seat will always be down on entry. Consider a semi countertop washbasin based wc so tiled boxing can extend full width of room at window wall. Mirror over basin should fit neatly between windows, giving great daylight for washing / make up etc... Hope this helps.

1) if you can, rehang the door so it opens the other way for a more efficient use of space. It enables you to use the space where your bath currently is for the loo without having to walk around the door.

2) the first thing you see as you come in should be the bath, on the wall under the window. If you have it built in, you may be able to include some crafty hidden storage within the side panels. You could even use a wainscoting around the bathroom that matches the fron bath panel. You could tile (or tongue and groove if you like things a bit country) up to the window.

3) on the right as you come in, (left of your diagram) have your sink unit (in between the bath and loo) . Have your towel warmer/radiator on the other wall.

I've mocked it up in Room planner for you, but have used standard sized loo, sink etc. You may want to use slimline/cloakroom sizes to get the best use of space.

Are you able to relocate the door? If you can, I'd move it to the 113cm wall. This will allow the bath to move between your existing door and the outside wall (should have just enough space). You can then have toilet beneath the window and the wash hand basin on the side wall. The awkward corner can then be used for some bespoke shelving/cupboards as it looks as though storage is an issue for you at the moment.