Electrical gremlins

[Neilx300]

Good evening to all. Thank you for letting me join JEC, I am a new member as of today.
I have a lovely x300 but am experiencing some electrical issues. I bought the car from an American who flew back to the states with the remote key fob. This was not an issue, I just used the keys provided and all was fine.
The battery went flat over a period which set the car alarm off. I replaced the vehicle battery but the car still thinks it’s alarm should be going off, as soon as I connect the new battery the hazards, headlights etc all flash. The car starts, runs and drives, but I cannot stop this alarm mode! Further to this, the engine starts just by inserting the key and turning to position one. I need to programme a new remote fob to se if the car responds. If I manually lock all the doors, and use the key in the drivers door, the car chirps as the central locking opens, but this doesn’t stop the lights and hazards.
Does anyone have any tips on what I can do, or a name of anyone who might be able to help?
Thanks in advance
Neilx300