As others have said here and we’ve covered in quite a few threads before, the number one protection for a Cali is to keep your keys safe. That’s not in a bowl by the front door, not hanging up on the kitchen, but safe, out of sight. We do this with all our cars.
I’m not sure about T5 Thatcham for the immobiliser and alarm, but for a T6.1 it’s as high as you can get and without the key, impossible to steal without a crane or low loader.
I did some digging a year or so ago and found, based on the data available, about 9 Calis were stolen (I can’t recall which year). One would hazard most of those were through the keys being stolen. The majority of theft stats for vehicles is theft from, not of.
Outside of keeping the key safe, just about everything else is either a deterrent against theft attempt by a nugget who thinks you can still hot wire cars (steering locks, bear locks etc) or peace of mind for you. Which is fine.
But, IMHO, Ghosts are utterly pointless. If someone is in my house, finding my key safe, breaking into that, getting the keys and going outside to steal my car, assuming I haven't got downstairs with my baseball bat in time, they are welcome to the car. It’s insured. I have more chance of winning the lottery though than that happening, so I rest easy at night. I also don’t buy a ticket
As an extra aside - your worry is not unusual, just about every new owner comes on and worries about theft of what is a major purchase for them. Just let it wash away and dont get caught up in the website sensationalism of these sellers - they have stuff to sell.
