\\\\All I'm asking is can a GP request a CT scan without referring a patient to a consultant?\\\
I hope not.
It is often difficult for a GP to decide which is the better investigation MRI or C-T scan and the wrong investigation may be performed with waste of time and money.
When the result of the investigation is available in almost all cases, the patient THEN has to be referred to the appropriate Consultant, thus wasting time.
I would imagine that very few if any NHS units could cope with the volume if open house id given to the GP.