John, you are right. It is better to wait until September, as you'll get it extended two years from the date of expiration, not from the date of getting the examiners signature.
In other words, if you go to an examiner now (either an FE or CRE, doesn't matter), you'll get extended until july 2013, whereas you wait until september, you'll get it extended until december 2013.
Can't explain it, but that's how it works.
And yes, according to JAR-FCL and the ANO, any flight with an instructor counts, as long as it's over one hour and logged as PU/T. LASORS confuses the issue by saying that it needs to be a revalidation flight, with purpose and objectives made clear as such, but to the best of my knowledge that LASORS "advice" has no basis in any legal text. So if the purpose of the flight was tailwheel training, or even if you were just bimbling about with your instructor friend, and you decided to both log the time (he/she as PIC, you as PU/T), it counts. (That last example might not have been the spirit of the whole idea, but it is 100% legit as far as I know.)