Your UK lifetime PPL should still be valid so its only a matter of
replacing the paper Airman Certificate for a plastic one for a $2 charge.
It may be more convenient however to have it based on your EASA licence in which case you will have to rescind the old one and pay for a CAA licence validation (£45?) and optionally use the facility to get it done in person at Gatwick CAA/Belgrano.
Edit: It looks like you have to get a CAA validation either way, so you may as well get one issued based on your EASA licence.