So I experienced issues with my car alarm and interior boot light which I think maybe a common failure point on f30 3 series. I have since managed to fix the problem and wanted to share how I fixed it for pretty much no money. So if you have a similar issue you can fix it without going to a mechanic or dealer.
1. What I was experiencing
The problem I was having was that when the car was locked and and I opened the boot using the fob, keyless entry (into the boot) or the foot swing under the rear bumper when I shut the boot again the alarm would go off (providing the car was still locked). This was really annoying and embarrassing especially when i was showing off comfort access to my mates.
A second problem was that the interior boot light wasnt coming on even though I checked the fuse and bulb was fine.
2. The problem
The broken component was the boot latch itself, which had some broken plastic which prevented the latch staying in the open position, this meant the sensor inside couldn't tell if the boot was open or closed.
the reason this could be a common fault is that if something is in the way of the latch when closing it is likely the brittle plastic will break meaning the sensor will stop working. Which seem quite likely to me
3. The fix
To fix it I simply used some epoxy to glue a plastic stopper tab onto the latch so the sensor could recognise when the boot was open. This fixed the light and alarm problem and cost me £0 as I had the glue lying around. A more permanent solution would be to buy a replacement latch which I may well do as they look to be around £20 on ebay but for now this will do. This fixed the Interior light and the alarm problem as the car now knew when the boot was open or closed.
Hopefully this is helpful to someone.