Immobiliser problem

Hope everybody has had a good Christmas.

Just before Christmas I got my 07 VRS back from having a hybrid turbo fitted.

Since getting it back from my mechanic the immobiliser has been playing up, I can lock the car and open the boot from the key, but I cannot unlock it unless I use the lock on the drivers door.

When I unlock it from the door, the red light on the popper still flashes, and when I turn the ignition on the alarm sounds one beep then goes off along with the red light on the popper.

It's not too much of a problem but it's highly annoying when I need to go somewhere when everybody is in bed!

If anybody has any ideas what has happened I'd be highly appreciative of it!