NC factory car alarm

[Bravo203]

I have a 2007 NC which has a factory (high spec) alarm fitted. Recently, the alarm has started going off in the garage about 1am or 2am. The doors were locked, windows up and no chance that anyone or anything got into the garage to set it off. The bonnet switch for the alarm is working well and the car battery was replaced only a few months ago (Century battery).

I think it might be the rechargeable back-up battery in the siren that has failed. Maybe??
I tried to get a replacement battery for it but the guy at Batteryworld said that no-one sells them. He sent it away to get a duplicate battery made but the quote was $150. It's just 4 button batteries with 2 small wires leading into a plastic connector.

I have removed the siren, so no more early morning wake up calls for me or the neighbours. And I thought about taking out the rest of the alarm altogether.

My question (finally) - if I remove the factory alarm, will I lose the keyless entry function?

Sam