Worth persevering
As an aspiring FI with PPL only, FI/CRI and studying for CPL TX. Instructing is not an easy alternative, there are plenty of well qualified ATPL/ CPL’s out there but I believe it’s worth persevering and there is a role for PPL instructors. The exams are easily proven, the onus is on the job applicant. For a small fee the CAA will verify theoretical exam results. The exam expiry period is only in relation to pursuing a CPL or ATPL, the written can stand alone.