Ok, thanks everyone, time for an update. I went back today and the exit chime is sorted - it was as simple as changing the program to "final door" exit mode, not simply "timed". Seems the former does a chime at the end, and the latter doesn't. I chucked a new battery in while I was there.
Regarding the circumstances...yes, I was doing a favour - I took pity on a charity who have an interesting old building (former boarding school). I was there for unrelated business and noticed "NVM CHECKSUM FLT" on keypad (I still can't avoid looking at panels after almost 10 years out of this trade) and commented they should get this seen to, and then replace the system. They replied they had no service contract, only the business card of the installer which is now "number not recognised", and that another company had declined to quote for replacement. It's a heck of a building with chunky walls and lots of tiled floors (even on 1st floor) and I can see the challenges. So I said if they can cope with external bells ringing for a minute there is a fair chance I can get it going IF there was documentation inside the panel. So I opened up (no tamper as it was crashed), found decent list of zones and program details, so took the usual steps to reduce the noise a bit, reset it and set the thing up again for them. So for now they at least have something working with an autodialler that calls their own staff. All the time saying "this is to buy you time, don't rely on this working for long".
Of course, that then prompted the next question; could I could fit something 'modern and better' for them and I agreed to look into options but haven't promised. As I don't have loads of time to play at my old job I'd rather they got a new pro install with service contract and have told them this. The only thing I could do for them in the time I have to do it would be reusing the iD wiring (it's 6 core btw) or possibly use a hybrid panel with expander initially with current iD setup and migrate to wireless as time permits. Neither is ideal from their point of view. I have a feeling that now the Karimza+ works again an upgrade will slip their mind until the next issue with it (or next thunder storm!) so we'll see what happens.
Thanks again for help and suggestions, I appreciate it.