We say yay, and we agree with @mudsi. In theright room, sinks can be so handy, and as a former renter in a 6 person house, a sink in a little bedroom can really ease morning bathroom traffic jams, as noone has to wait for that one person to finish showering to brush their teeth! However, I do think they have to be either well blended into the room or even hidden in a cupboard, as a random sink shoved into the corner of a room looks like a plumbing mistake!

I would not worry about putting a modern acrylic freestanding bath with a ceramic basin - the majority of our customers who buy freestanding baths opt for ceramic basins and they look great together. Acrylic freestanding baths offer lots of advantages over other materials - they're light and easy to move (many people don't consider how problematic it could be to actually get the bath into their upstairs bathroom), they're strong, affordable and often offer better thermal efficiency when compared to stone or steel baths. In terms of carrying on the design consistency in your bathroom suite the most important thing is ensuring your toilet and basin match, so try to get the same range if possible. Of course, if you are buying a modern freestanding bath then try to get a modern basin and toilet that share some design elements.

Try this shop on etsy : https://www.etsy.com/uk/listing/578096137/cloakroom-basin-stand-colours?ref=shop_home_active_4&frs=1 We have one of their oval basins and are really pleased with it, the square ones are smaller though.

If you can move your loo across slightly to one side then this would give you a lot more scope for a sink. If not then we fit a wc and sink into our old house wc which looked narrower than your room! We had a wall hung cloakroom sink which was tiny and super narrow with the tap on one side. Didn't get in the way really. Will see if I can find a picture of what I mean