It might be possible to have a loo and a tiny basin under the stairs. This depends on clearances and whether the plumbing is possible.

Hi, yeah that might be possible but accessing the cloakroom through the bathroom isnt ideal. Do you think moving the staircase by 180 degrees could help?

Could you show where the bathroom is on the floorplan please? I can only see a washing machine and tumbledryer?

Yes if course, heres the upstairs.

Staircase remodelling or repositioning will attract a considerable cost, so if you are on a tight budget, I'd recommend leaving the staircase where it is. I know it doesn't solve your issue, but at least you can avoid costly work