In the States, East Coast Bowthrusters recommended a Vetus 7512 for my 1989 Nauticat 33. Their decades of experience and sterling reputation led to my enthusiastically writing a relatively reasonable check to them last spring.
After 1 season, I can say that the install was top notch, and more to your question, the thruster is properly sized and has served us well. No regrets. And very glad we went with the recommended size (Of course, YAMMD).