Please also remember that the FTO has to pay a fee on each credit card transaction. It is not unusual for this fee to be scaled in accordance with the size of the individual transaction - the larger the value of each transaction, the lower the percentage fee. As the student is paying off the card spend only once a month (hopefully) then there is little point in lots of individual and low value transactions every few days.
A good FTO will operate a little like your solicitor. The student pays a reasonable amount up front (at least a weeks training) which goes into a "client account" to be held in trust. It can only be "taken" by the FTO as the training actually progresses.
Check if your intended FTO can provide this type of surety.