@Shamal - Motor connections physically look and feel okay. The connection from the lower gearbox onto the motors may be slightly on the looser side of things but still fit snug onto the positive and negatives of the motor.
@strykerles - Yeah, fuse is still in tact after it spun. When it did spin, I was moving the selector plate with my hand to see if I could engage the trigger contacts and connection must have been made somewhere. It was only a single very short spin, as it it was semi-auto.
Also, just for reference I have attached an image. If you need any other images to assist do just let me know.
[EDIT]
Looking at the photo below, I have actually just noticed a possible issue.
The positive and negative wires flip from the tamiya connectors i.e. red (positive) from battery then goes into black (negative) from the back of the wiring harness. Could that be the issue?
Thanks,