Sorry to jump in on this but.....
No, most sparkies wont lay tile, however, they should install the mat, test for cont and note the readings,
Once the tile has been laid, he then returns, does another test to confirm readings then does all the final connections, fires it up and does the cert.
ANY electrical work in a bathroom is notifiable and Part P does not allow any sparkie to certify anyone elses work, UNLESS, he has paid at visit at various stages to make sure it all complies.