The Jensen Owners' Club

Can anyone recommend a good immobiliser for my Jensen Interceptor series 3? (note the car now has Holley Sniper EFI replacing the old carb). Also, want to fit a tracker too - any thoughts?

https://www.flickr.com/photos/markcjensen/albums

I've got these fitted to some of my cars http://www.tracker.co.uk expensive but seem to be very good, although I do receive occasional false alerts when I'm actually driving. (With two of the systems I have to carry a "fob" with me which sometimes doesn't get detected, hence the false alerts.
I'd rather have those than non at all !