The judge has the discretion as to whether accept any reports. (Many people convicted of involvement in the recent riots have been sentenced 'on the day', with no reports being called for). However the fact that the person is currently on 'judge's remand' is strongly indicative that the judge will require one or more reports to be presented.
If so, a probation officer (and possibly others, such as a psychiatrist, depending upon the reports called for) will visit the person in prison to go through the report process.
Chris