I have been disqualified from driving, however can I still supervise a learner/sit next to them whilst they practice?

No. In order to supervise a provisional driver, you must have held a full licence for at least 3 years, the licence must remain valid, and you must be at least 21 years of age, unless you are a member of the armed forces acting in the course of your duties. The 3 year requirement does not apply to the supervision of large goods or passenger carrying vehicle provided the other requirements are met.