Hi,
Many thanks for your messages. Your key programming theory is quite possible, I bought the car just over a year ago, came with very little history, only has one key and the central locking has been playing up, off and on, for most of that time.
I suppose trying to clear the old unit with a Tech-2 is really a non-starter, as we don't seem to be able to get them to communicate, so a replacement module is the only way forward. Assuming I can get a complete set of module, fob and code, is that likely to cause any future problems if, as you say, the alarm and immobiliser will end up with different pass codes?
I note from elsewhere on the Forum that you offer Tech-2 Services!! The guy I use is a very good all round, all makes problem solver, but he is no particular expert on Vauxhalls and seems to favour using his Chinese gizmo to his proper Tech-2. So I'm thinking, when I've sourced the necessary bits, and the possibility there may be things to be programmed or other faults to be discovered, could I bring the car up to you to give it a good going-over with your Tech-2?
Many thanks for your help so far,
John