So, you will probably find that you still need a training flight as this has to be with 3 months of the revalidation. Good luck, hope this helps. (You can download the full Lasors as a PDF for free from the CAA site)
Nope. The training flight can take place anywhere in the preceding 12 months.
You need an examiner (not an instructor) to sign the paperwork (SRG\1119 comes to mind) before the class rating expires otherwise the process becomes different and a revalidation by experience is no longer possible.
The validity of the SEP class rating is two years from the moment the examiner signs the paperwork (rounded up to the nearest month I believe). But if the examiner signs the paperwork in the three months preceding expiry, the validity is until the original expiry date plus two years.