Can you post a pic of the keypad and alarm box?
I think your system will be the Eurosec CPX withe the wireless receiver as the CP8L is not compatible with Risco wireless devices.
From reading your post it looks like there are wireless devices that need the battery changing. Do you have 2 types of PIRs or door contacts in the property?
Without the user code (5678 default) there is not much you can do as I would advise you to look through the log to see what has happened.
The panel can be defaulted to the 5678 code but if the engineer code is locked then there is not much you can do as this will not default the engineer code and if the panel is on engineer tamper reset you will need the code.
I would google on how to reset the user codes to start with, change the panel battery, wireless devices batteries and see how it goes.