Glad that the interview went well, M&S are really good company to work for!
To be 'on hold' within a retail environment doesn't necessarily mean that you'll get a job within the next month or so. You'll have been in the Christmas recruitment pool this time, but it's likely that they've filled the positions. The next intake is usually in late spring or early summer.
It's amazing that you've passed the interview process, and it'll be great experience, but it may not be to your advantage that you call them daily. Rather wait until they contact you with a contract that matches you.
Also it may be wise to look for another job in the meantime, as like I say it might not come through for a while yet!