I'm with Gott & Wynne and they assure me that there is no requirement for either an alarm or tracker on my new +8.
Worthers +8
Exactly the same, no tracker and no alarm, G&W said that the BMW Immobiliser is enough. They provided cover with unlimited mileage, personal business use and an insured value of £79,000.
A further comment: when it looked as if I'd have to get an alarm I talked to a very experienced fitter, he told me that alarms can only be fitted in a limited way to soft top cars, just tilt and movement sensors.
He said on the phone that he could wire the alarm into the door switches and seat sensors so if the door is opened or the anyone sits on the seat it goes off. Also there are proximity sensors that might work, they detect people as they approach.
Then when he actually looked at the Plus 8 he said "forget it": the bonnet needs to be secure to protect the control box. He couldn't work out how to fit anti tamper micro-switches to the Morgan bonnet.
Bottom line: for an alarm to be accepted by an insurance company it has to meet specified criteria of coverage and resistance to tampering. He couldn't see a way to achieve this with a Morgan so the installation wouldn't be accepted by any insurer.