Thanks for your reply, the problem was that when I was filling in insurance information on go compare website it automatically put in that my car had thatcham alarm fitted as if that was normal for Mercedes cars, after looking through the manual I discovered that was not the case, I should have looked there first, sorry for the trouble.
Shows all Mercedes B Class vehicles built from 2005 as having a Thatcham approved Cat 1 alarm.
N.B. Insurance companies usually ask about the alarm in order to ensure that the vehicle owner knows that it is working (has not disabled the alarm nor by-passed the immobiliser).