I think the problem with my question is that the question is incredibly vague i.e with regard to lack of weather information from the departure point and further prevailing conditions. It isn't even clear where the aircraft if returning from, so might be worth me asking my instructor so that I can give a more defined answer.
Conversely, he might want me to discuss the difference in outcome between a long a short return sector. SO MANY VARIABLES and it's certainly ambiguous whether the aircraft should be tankered or not. Also, I presume company SOPs may or may not allow for tankering into a contaminated runway as Hoppy has said.
Finally, the question states that the flight takes place in temperature's at a constant -15 degrees OAT. Do I assume that includes being at cruise altitude, it seems quite warm when the aircraft might be operating at an altitude of 33,000ft.