What do you mean by a 'nearly out of date PPL'? Is it your licence which needs to be re-issued at the 5 year point or your SEP Class Rating which is about to expire?
The Vigilant is not a SEP Class aeroplane. Neither is it a SSEA Class aeroplane for NPPL purposes. Either you will need a TMG Class Rating on your JAR-FCL PPL(A) or a NPPL SLMG Class Rating in order to count time on Vigilants; but, at present you would have to maintain both SSEA and SLMG NPPL Class Ratings independently.
I suggest you revalidate your JAR-FCL SEP Class Rating by LPC, then add a TMG Class Rating after which hours flown on either a SEP Class aeroplane or a TMG Class aeroplane will count towards the validity of both Ratings