I would have agreed with you however reading AIC White 001/2011 it states:
Note: Training for the initial issue of an NPPL, PPL, CPL, IMC Rating, Instrument Rating or other 'ab initio' training is not permitted. The
intention is to allow individuals to pay for training that enables them to regain currency, renew a licence, learn a new skill (such as
short field landings) or become familiar with a new type etc.
Which raises an interesting point, you are talking about a Class Rating which is effectively a new type.
With any Permit aircraft you need to see if Aerial Work (Flight Instruction) is permitted, if not you have your answer.
Does your candidate hold an NPPL with a Microlight rating or a PPL (Microlight) issued prior to the NPPL? If its a NPPL you are doing Class Rating training so as its not specifically forbidden. If he has an older PPL (Microlight), will this training result in the initial issue of a new licence, and if so does that constitute ab-initio training? If it does, as a CRI you are not eligible to do it.
Now see what you've started!