Hi Sean. WE got one like that in last week, Tried used ecu, still the same, tried used immobiliser box, still the same, spent a couple of hours checking everything, then tried a new immobiliser box and off it went, If you fit an immobiliser box, I think you just put ecu into learn mode and it learns the signal from the immobiliser, then just programme remotes as normall. Ecu firm could have bypassed the immobiliser for you whilst they had got it, to eliminmate it from your enquiries.