I can advise from the other side of the coin if you wish - did a Social Policy degree with years placement, and several holiday/work experience sessions through degree.
One thing to bear in mind is the length of preparation time - i.e. sandwich placement job applicants will be looking for the job from September the year before. While there is no reason you couldn't recruit in May/June for an August/September start, most of the good students will have been snapped up by jobs whose applications opened in the previous September/October/November.
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