Basically the old frequencies are more subsebtle to types of interference, hence why better to update , not just alarms mind you , when they shifted the frequencies for what they are used for quite a few things were updated by manufacturers and it just depends on how much of a priority it became for an individual or organisation to follow suit and update
Out of curiosity, did your alarm used to chime? As above its an old panel and its totally incorrect to say that not much will go wrong
This is a good time to update it , May work out cheaper as you have cables in place and May work out
Give your front door sensors a slap while your at it...... I learnt that from someone here, or get a hole cutter and I explain what to with that later
You said you have small cable access, run two if you can , or a "bigger cable" ideally an 8core for the bell and "bigger cable" for the sensors upstairs , try and buy cable made by cqr , probably other manufacturers to,
I think that is what you should start with, if the cables don't get in then you can opt for buying different equipment
Come on.... Means the word should be sensored.
Ok in the small space you have, you could run two 8cores up to serve the sensors and bellbox upstairs
And wireless elsewhere , or depending on how close panel is to front door sometimes you can get an 8core to the front door , especially if it's in the understair cupboard
Problem now is there's no manufacturing , electronics has changed , so course demand dropped , few years back they pushed ict to be the way forward, recently they back tracked
Overall what happen in many trades "skills shortage"
New generation are not trained the same way
Use a digital meter easier than having to listen......
It's simple case of getting your wiring right and resistors in the correct place
If you want to do a course do a basic course , do one in very basic electronics it will help allot with fault finding imo