Cannot lock Alarm goes off - Convenience Control Unit

Hello,

Our Fabia II has  issues with the central locking/alarm system.

When you lock the car it will unlock itself or trigger the alarm at random intervals and when you drive the car it will continue to lock and unlock itself even whilst moving. 

The only way to stop this is to remove fuse 45 for the convenience control system thus removing the power to the central locking etc. But that means the car can never be locked!!

Taken it to a local garage and they replaced drivers door solenoid which was damaged by water ingress which was picked up as a fault code. This still hasn't fixed the alarm issue and the garage consulted main dealer who are guessing the "body control unit" (convenience control system?) has also been damaged and needs replacing.  apparently this has to be done at a main dealer and the unit costs £450 + £200 fitting charge. 

Does anyone know if the convenience control unit can be simply replaced (there are second hand ones on eBay) or will this need programming?

Thanks for reading!

P.S. my issues sound the same as this post but I haven't been able to get a reply to find their outcome...