I used London Structural Design for my bathroom a few years ago. Robert has a fantastic eye for detail and aesthetics. We have quite a small bathroom and so he helped us maximise the space by advising what size toilet/shower/sink we should buy. He suggested some cupboards and a really chic counter top that he built. It wasn't cheap, but he is reliable and spots issues before you even do. There is nothing sloppy about this guy - his attention to detail is fantastic even with regards to areas that you can't even see (like behind the toilet for example). He also did extensive work in my previous flat including a bathroom refurb. His website is: https://www.londonstructuraldesign.org.uk/
He has a few guys working for him who do the bulk of the work, but he does all the design and management, etc himself.