Motorhome Security - Risks

As many of you know we are relatively new to motorhoming, buying our first one earlier this year. Whilst ours has an engine immoboliser it does not have an alarm. ( I previosly asked about alarms so I am not asking specifically about those) I am interested to know from members what they consider the security risks to be with a motorhome. We generally stay on sites and tend not to take the motorhome out once on sites. An alarm is a hefty investment and I wondered what other security options are suggested. Also what would be considered the weak points from a security perspective of a motothome, cab doors or habitation doors or is it windows?

David