Stephen
With 200 hours you no doubt have a UK PPL valid for life in which case it will never EXPIRE. Within the PPL you have a Medical Certificate that will expire and an Aircraft Rating that will expire.
The aircraft rating can be revalidated or renewed simply by passing a proficiency check as described by Gone West. Rather than rushing to get 5 hours, just do enough to feel comfortable and do a prof check, that revalidates the aircraft rating for another 24 months.
If you do deceide to get the 12 hours you need in the 12 months prior to the rating expiry, you must also have the licence signed by an Examiner within the validity date or it will expire and the hours will be no good - then back to the prof check again, but now called a Skill Test.