Astra mk5 door lock

Hi the rear offside door of my Astra will not open as normal, as though the central locking is still engaged, I managed to open it by using the inside lever, while the C/L was engaged, but not otherwise, I assume that the solenoid has failed and needs replacing, do I need to replace the complete unit?. while the door is open, and I use the key pad I can hear the lock operating, my pet hate with car diy is removing trim, I always finish with a load of broken clips etc. any ideas please

Purchase yourself a set of trim removal tools. I used to cause damage to clips etc. by going at it with screwdrivers and other metal implements. With trim tools, not only do they not damage the plastics, they are quite delicate themselves, so you need to take it easy.
Once the door card is off, you may be able to see the problem.

Pull back the rubber boot where the wires go into the door as they have a common problem of breaking wires in there