Hi Guys, an update to the problem I'm having, today I've pulled the door card off the affected door, disconnected the latch from the power and tested it. There is power going to the door, once I'd reconnected everything back up and attempted to lock the car, it locked but then automatically unlocked itself and continued to do this until I manually locked the affected door, after locking that door I then attempted to lock the remaining key from the remote with success.

I'm now pretty confident it is the latch/solenoid itself that is causing the problem, could someone confirm that this is the problem or if there's something I'm missing.