I just had to look at this toilet brush thread [I mean, it seemed so unlikely] However,overthethill last year I did exactly the same as you [great minds think alike.]Fed up with brown brushes, bought a couple from Sainsburys, as you say the slightly curved ones and a bit smaller, they do a great cleaning job, and they are cheap, no need to replace the bowls they sit in, a good solution all round.
On washing pets dishes; you have to do it somewhere but I would never use my washing up bowl, used to take that out and then clean the pet dishes in the sink.