'Despite being a civvy QFI 17 years ago'
Ah - that explains things! In which case you just needed to renew your SEP Class Rating and renew your FI Rating (there is no such animold as a 'civvy QFI'). Regrettably, that does require seminar and test.
I agree that military QFI-ing on the Tucano (a SET Class aeroplane, surely) should certainly be viewed more favourably by the CAA. They know that the PPL world is getting increasingly short of FIs and to include the A2 Cat on the Tucano as part of the 'recognition of skills and experience gained in military service' would seem entirely reasonable to me as one way of reducing this shortage.
Perhaps CFS Exam Wing could broker the case?