The licence issued to you for life will be with you for life.......even if you get another licence eg a JAR-PPL isued on the basis of it.
You never have to hand back your for life licence.
Having said that, the licence is useless without a medical and valid rating(s).
So if the CAA was to say to you you can have your licence for life but the ratings which are not for life can not be revalaidated unless you hold the appropriate licence - a European one ends the argument.
There are always plenty of ways round such "problems".
Regards,
DFC