Hi, You don't think the "sink unit " was meant to go against the right hand wall, beside the black box that could be the wastes from the right side bathroom. And not as usual at the window area. Strange but you know what builders are. Maybe there is already an input fitted to that stack but blocked up at this time. Flexible camera comes to mind now. Interesting my dear Watson. This is a 2 pipe puzzle . Have fun, Johnny M
I would look at the plans they should give a good clue where the sink was to be located and then look for signs of the 1st fix
All sorted. There is a drain immediately under the window. Also there is a waste pipe connected to the soil pipe under the upstairs bathroom. Cracking on.
There's quite a bit not finished, or of questionable quality, but in all decent house. An example being the electrical outlets and there gaps below / above