While my previous posts refer to the IR35 compliance for those registered as Ltd companies, I hadn't considered the sole trader case.
However I would still argue a similar case, that even for to be self employed you have to be able to control your own working hours, a restricted instructors hours are still determined by the supervising instructor. That is he/she cannot continue to work if the supervising FI chooses to leave early.
Therefore R44, my interpretation of the rules is that you would only be able to register as a sole trader when you have your restriction lifted. This means your intitial terms as a instructor would have to be on an employed status.