Vauxhall have issued a high level security risk for Vehicle central locking systems on ALL vehicles with remote control keyfob locking.
Theives are using mobile phones to 'record' your keyfob transmission and then transmit the recording via text message to unlock or lock your vehicle.
Try it, it works.
Write a text on your mobile phone (leave it on the phone and do not send it just yet)
Then press your car key open button whilst next to your phone
Then send the text to anyone in your phonebook.
As the text is sent it also stores your unlock code in the text transmission.
When your friend returns the text to you it will unlock your car!