Although ban-all-sheds is (as usual) correct, he does have a tendency to be quite curt in his replies. The shower you have installed requires at least 41 Amps of supply capacity at 230v, more if your supply voltage is a little higher, which in the majority of cases it will be.
While it's obvious you will require an MCB of a higher rating, it's also clear that you don't have the necessary experience to carry out this install, otherwise you wouldn't be here in the first place. How do we know that the rest of the installation is safe? It seems unlikely you've performed anything other than a functional test, or that there's been any thought gone into circuit design. We don't even know if the cable is the correct size for the job.
Please, for the sake of your family, call in a qualified electrician who is a member of a self-certification scheme - before an electrical fault burns your house down or someone gets electrocuted in the shower. This work is notifiable anyway, so having carried it out without first informing your local building control, you are in breach of part P of the building regs.
