You’ll need to make sure the “new fob” works at the same frequency as the existing one. Then you’ll need a new transponder for the fob and have it programmed to your immobiliser. Then you’ll need a new blade cut and fitted to the fob.
The programming of the transponder needs to be done by someone who can read your cars Secret Key Code (SKC).
I think 2 members can carry out this work for you, and they’ll be able to confirm what you need to do, they are:
Sarge768 – based in London
And
Skipton01 – based in Lancs
Might be worth dropping them a PM.
Cheers
Jeff