In summary: If you have completed your 12 hours (of which must be in the closing 12 month period!!!) and you are now in your second 12 months then sort out a flight with an instructor - as soon as the closing 3 months begins, get your license signed too.
Unless I'm reading JAR-FCL 1.245 wrong, I don't think you even have to wait for the closing 3 months. The revalidation by experience can take place, without loss of validity period, at any time in the second 12 months.