Unless you are a CFS graduate, you cannot be a 'Q'FI. What you seek is to 'renew' your lapsed rating to become a FI(A). As we're now into JAR-FCL requirements, you will have to pass a flight check (£150 Examiner's fee as well) which also includes a ground element rather longer than the old UK FI revalidation. You will also have to do the 2-day seminar, typically run by folk such as The Examiner Training Agency (
www.flightexaminers.com ) costing about £195+VAT excluding overnight accommodation. You will also have to study JAR-FCL and JAR-OPS in order to sign the declaration of knowledge required before you may teach for JAR-FCL licences. See AIC 55/1998 for details. Then , to keep your FI(A) rating valid, you will have to do 2 out of 3 requirments: 100 hours instructing in the 3 years of the rating's validity period including 30 hours in the last year, revalidation proficiency check, 2-day seminar.